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  • Analysis of silicon wafer surface preparation for heterojunction solar cells using X-ray photoelectron spectroscopy and effective minority carrier lifetime
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2018-03-12
    U.J. Nsofor, L. Zhang, A. Soman, C.M. Goodwin, H. Liu, K.D. Dobson, U.K. Das, T.P. Beebe Jr., S. Hegedus

    We report a systematic study on the optimal conditions for silicon surface preparation to ensure excellent passivation at the crystalline-amorphous silicon (c-Si/a-Si:H) interface of silicon heterojunction solar cells for both untextured and chemically textured samples. X-ray photoelectron spectroscopy (XPS) was utilized to analyse the elemental composition of known silicon impurities on the wafer surface. Surface purity and passivation quality, characterized by effective minority carrier life time (τeff) and implied open circuit voltage (iVOC), were estimated using either quinhydrone-methanol solution or 10 nm intrinsic a-Si:H layers deposited using DC plasma process. This study confirms that surface damage etch (SDE), tetra-methyl ammonium hydroxide (TMAH) texturing and the subsequent TMAH residue removal are the most critical steps in the cleaning process, supporting a simplified wafer cleaning approach that is concise, repeatable and uses minimal volume of chemicals.

    更新日期:2018-03-12
  • Exploration of graphene oxide nanoribbons as excellent electron conducting network for third generation solar cells
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2018-03-06
    J. Kusuma, R. Geetha Balakrishna, Siddappa Patil, M.S. Jyothi, H.R. Chandan, R. Shwetharani
    更新日期:2018-03-07
  • Fatigue crack growth in Silicon solar cells and hysteretic behaviour of busbars
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2018-02-23
    Claudia Borri, Mariacristina Gagliardi, Marco Paggi

    Photovoltaic modules are subject to cyclic deformation during their lifetime as a result of vibration, applied loads, and thermal effects. Vibration and applied loads induce cyclic bending on the modules, while operating temperature excursions during the day lead mostly to cyclic axial deformation. In both cases, the region between two solar cells is severely stressed. For cyclic bending, cracks can nucleate near the points where busbars are soldered onto Silicon and might propagate due to fatigue. For cyclic axial deformation, on the other hand, busbars are stressed above the elastic regime and may experience plasticity and hysteretic energy dissipation. The present study focuses on the experimental characterization of such material degradation phenomena related to the above two types of cyclic deformation. For the former, fatigue crack growth in Silicon and its evolution have been quantified by using two independent nondestructive monitoring techniques based on electroluminescence and thermal infrared imaging. For the latter, plasticity and degradation of the material response of busbars has been assessed in relation to different applied cyclic strain levels. The obtained results shed light onto the cyclic response of materials used in photovoltaics, and pinpoint features that should be taken into account in the development of refined standard qualification tests for photovoltaics including cyclic deformation.

    更新日期:2018-02-23
  • Advanced light management techniques for two-terminal hybrid tandem solar cells
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2018-02-23
    A.J. Blanker, P. Berendsen, N. Phung, Z.E.A.P. Vroon, M. Zeman, A.H.M. Smets

    Multi-junction solar cells are considered for various applications, as they tackle various loss mechanisms for single junction solar cells. These losses include thermalization and non-absorption below the band gap. In this work, a tandem configuration comprising copper-indium-gallium-di-selenide (CIGS) and hydrogenated amorphous silicon (a-Si:H) absorber layers is studied. Two main challenges are addressed in this work. Firstly, the natural roughness of CIGS is unfavorable for monolithically growing a high quality a-Si:H top cell. Some sharp textures in the CIGS induce shunts in the a-Si:H top junction, limiting the electrical performance of such a configuration. To smoothen this interface, the possibility of mechanically polishing the intermediate i-ZnO layer has been explored. The second challenge that is addressed, is the significant current mismatch in these tandem architectures. To enhance absorption in the current-limiting top cell, the ZnO:Al front electrode was textured by means of wet-etching the entire tandem stack. We demonstrated that one can manipulate the morphology of the random textures by varying the growth conditions of the ZnO:Al, leading to better light management in these devices.

    更新日期:2018-02-23
  • Development of porous TiO2 nanofibers by solvosonication process for high performance quantum dot sensitized solar cell
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2018-02-13
    Nisha Singh, Zaahir Salam, A. Subasri, N. Sivasankar, A. Subramania
    更新日期:2018-02-14
  • Optimization of DMSO-based precursor solution by H2O additive for performance enhancement of kesterite photovoltaic devices
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2018-02-13
    Yun Zhao, Xiuxun Han, Le Chang, Jiajia Li, Chen Dong, Yi Fang, Junshuai Li
    更新日期:2018-02-13
  • Scattering enhanced quantum dots based luminescent solar concentrators by silica microparticles
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2018-02-10
    Haochen Liu, Shang Li, Wei Chen, Dan Wang, Chen Li, Dan Wu, Junjie Hao, Ziming Zhou, Xinzhong Wang, Kai Wang

    Luminescent solar concentrator (LSC) integrated with c-Si photovoltaic cells (PV cells) in building integrated photovoltaics (BIPV) could grow up to be an important element of our life for energy harvest in the future. Heavy metal free quantum dots (QDs) are promising for LSC applications, which can be controlled to possess effective large Stokes Shift and low reabsorption of emission that benefit their applications in BIPV. In our work, different amount and size of SiO2 particles were added to CuInS2/ZnS QDs based LSCs to realize highly efficient scattering enhanced LSC (S-LSC) devices. Since SiO2 particles induced scattering effect, we achieved a power conversion efficiencies (PCE) of 4.20%, which showed an improvement of 60.3% compared with the pure QDs based LSC without SiO2 particles. This study suggests a new method of scattering enhancement to realize better performance for LSC.

    更新日期:2018-02-10
  • Management of light trapping capability of AZO film for Si thin film solar cells-via tailoring surface texture
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2018-02-10
    Yanfeng Wang, Jianmin Song, Lisha Bai, Fu Yang, Bing Han, Yajuan Guo, Binting Dai, Ying Zhao, Xiaodan Zhang

    In this paper, novel micro- and nano-composite Al-doped ZnO (AZO) films with broadband-gap light-trapping capacity was successfully fabricated by post-chemical-etching AZO film and re-sputtering self-textured H and Al co-doped ZnO (HAZO) film. The influence of pressure and etching time on the optical and electrical properties of HAZO, AZO, and AZO/HAZO films were systematically investigated. The performance of this novel ZnO film was increased remarkably compared to that of the post-etched AZO film or native textured HAZO film for both long and short wavelengths. Microcrystalline silicon solar cells deposited on this new type of AZO/HAZO films exhibited a strong enhancement of 13.4% in the conversion efficiency, demonstrating its wide application prospect.

    更新日期:2018-02-10
  • 更新日期:2018-02-10
  • Properties of mixed phase silicon-oxide-based passivating contacts for silicon solar cells
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2018-02-07
    I. Mack, J. Stuckelberger, P. Wyss, G. Nogay, Q. Jeangros, J. Horzel, C. Allebé, M. Despeisse, F.-J. Haug, A. Ingenito, P. Löper, C. Ballif

    We investigate the properties of an electron selective front contact based on a phosphorous doped mixed-phase SiOx SiO x /Si layer stack at device level. The addition of the SiOx SiO x phase to the Si layer targets reduced optical absorption, pursuing the goal of a broad-band transparent full-area passivating contact for front-side application. To demonstrate the validity of our approach we realised a planar hybrid solar cell with the mixed-phase SiOx SiO x /Si-based passivating contact on the front side and a hydrogenated amorphous (i/p) silicon heterojunction as rear hole-selective contact. With this structure, we obtained a VOC V OC of 691 mV, a JSC J SC of 33.9 mA/cm2 cm 2 , a fill factor of 79.4% and an efficiency of 18.6% on a planar n-type FZ Si-wafer. Temperature-dependent IV IV -measurements at solar cell level were performed in order to understand the physical mechanisms behind charge carrier transport and surface passivation of the mixed-phase SiOx SiO x /Si layer stack. The results were compared to those of a standard silicon heterojunction (SHJ) cell on a similar planar substrate. The temperature dependence of the IV IV -curves in the range from –100°C to +75°C reveals that the hybrid cell is less temperature sensitive with respect to the SHJ cell. Furthermore, at low temperatures, the analysis reveals a reduction of the VOC V OC temperature coefficient of the hybrid cell, whereas for the SHJ cell a saturation occurs. This behaviour hints that the barrier imposed by the SiOx SiO x /Si-based contact is less pronounced than the barrier imposed by a standard SHJ contact.

    更新日期:2018-02-08
  • Fast-switching all-solid state electrochromic device having main-chain 1,2,3-triazolium-based polyelectrolyte with extended oxyethylene spacer obtained via click chemistry
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2018-02-07
    John Marc C. Puguan, Amol R. Jadhav, Lilian B. Boton, Hern Kim

    A fast-switching all-solid state symmetrical electrochromic device was successfully fabricated using poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) as electrode and a poly(ionic liquid) based on 1,2,3-triazole with oxyethylene spacer as solid electrolyte. PEDOT:PSS solution was spincoated on ITO glass and annealed to obtain the electrode layers. Two different types of electrolyte were synthesized via copper-catalyzed alkyne-azide cycloaddition (CuAAC) using novel azide/alkyne-terminal monomers. These newly developed main-chain 1,2,3-triazole-based poly(ionic liquid)s having variable spacer length underwent quaternization using methyl iodide and subsequently allowed to make anion exchange with lithium bis(trifluoromethane)sulfonimide salt to obtain PILs with remarkable properties. The PIL bearing [–(CH2CH2O)6–] spacer showed a conductivity of 1.20 × 10−4 S cm−1 which is at par with best side-chain PILs in literature and it efficiently switches an electrochromic device (ECD) with 22% optical contrast from its transparent state to a colored state in 2.5 s and 3.2 s to return to its bleached state. Likewise, it exhibits excellent thermal and mechanical stability that is ideal for practical applications.

    更新日期:2018-02-07
  • Ultra-thin nanocrystalline n-type silicon oxide front contact layers for rear-emitter silicon heterojunction solar cells
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2018-02-06
    L. Mazzarella, A.B. Morales-Vilches, L. Korte, R. Schlatmann, B. Stannowski

    Hydrogenated nanocrystalline silicon oxide (nc-SiOx:H) films have demonstrated a unique combination of low parasitic absorption and high conductivity. Here, we report on the use of n-type nc-SiOx:H as front surface field (FSF) in rear-emitter silicon heterojunction (SHJ) solar cells exhibiting excellent electrical cell parameters at a thickness down to only 5 nm. Using a seed layer, we are able to maintain excellent electrical performance (high fill factor (FF) and open circuit voltage (VOC)), while enhancing layer transparency for maximizing short circuit current (JSC). These results, together with the short deposition time (< 100 s), make the (n)nc-SiOx:H FSF attractive for reducing production costs in industrial applications. The best device, with the optimized (n)nc-SiOx:H FSF layer, shows VOC of 731 mV, FF of 80.6%, JSC of 38.3 mA/cm2 and a power conversion efficiency of 22.6%.

    更新日期:2018-02-06
  • Improved efficiency of PbS quantum dot sensitized NiO photocathodes with naphthalene diimide electron acceptor bound to the surface of the nanocrystals
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2018-01-11
    Mahfoudh Raissi, Muhammad T. Sajjad, Yoann Farré, Thomas J. Roland, Arvydas Ruseckas, Ifor D.W. Samuel, Fabrice Odobel
    更新日期:2018-01-11
  • Modelling of flexible thin-film modules for building and product integrated photovoltaics
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2018-01-06
    N. Bednar, A. Caviasca, P. Sevela, N. Severino, N. Adamovic

    In this work we present a simulation of performance of curved thin-film modules for building and product integrated photovoltaic applications. Flexibility of design and possibility of achieving irregular shapes is important feature in these markets. The photovoltaic module model presented in this work is based on a coupled two-step model. The first 1D model describes the technology and outputs device current density in dependence of voltage, temperature, illumination, etc. The second 3D model uses this data as one of its inputs, and describes size, shape and interconnection of the individual cells within the curved flexible module. In this way power production of such photovoltaic system can be assessed in reasonable time and computing resources. Two study cases are presented: a dome shaped solar street lamp and a conic shaped active rooftop shading for a skylight.

    更新日期:2018-01-06
  • Controllable and large-scale fabrication of rectangular CuS network films for indium tin oxide-and Pt-free flexible dye-sensitized solar cells
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2018-01-05
    Zijie Xu, Teng Li, Qian Liu, Fayin Zhang, Xiaodan Hong, Shuyao Xie, Changxu Lin, Xiangyang Liu, Wenxi Guo
    更新日期:2018-01-05
  • 更新日期:2018-01-03
  • Light-trapping enhanced thin-film III-V quantum dot solar cells fabricated by epitaxial lift-off
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2018-01-03
    F. Cappelluti, D. Kim, M. van Eerden, A.P. Cédola, T. Aho, G. Bissels, F. Elsehrawy, J. Wu, H. Liu, P. Mulder, G. Bauhuis, J. Schermer, T. Niemi, M. Guina

    We report thin-film InAs/GaAs quantum dot (QD) solar cells with n−i−p+ n − i − p + deep junction structure and planar back reflector fabricated by epitaxial lift-off (ELO) of full 3-in wafers. External quantum efficiency measurements demonstrate twofold enhancement of the QD photocurrent in the ELO QD cell compared to the wafer-based QD cell. In the GaAs wavelength range, the ELO QD cell perfectly preserves the current collection efficiency of the baseline single-junction ELO cell. We demonstrate by full-wave optical simulations that integrating a micro-patterned diffraction grating in the ELO cell rearside provides more than tenfold enhancement of the near-infrared light harvesting by QDs. Experimental results are thoroughly discussed with the help of physics-based simulations to single out the impact of QD dynamics and defects on the cell photovoltaic behavior. It is demonstrated that non radiative recombination in the QD stack is the bottleneck for the open circuit voltage (Voc V oc ) of the reported devices. More important, our theoretical calculations demonstrate that the Voc V oc offset of 0.3 V from the QD ground state identified by Tanabe et al., 2012, from a collection of experimental data of high quality III-V QD solar cells is a reliable – albeit conservative – metric to gauge the attainable Voc V oc and to quantify the scope for improvement by reducing non radiative recombination. Provided that material quality issues are solved, we demonstrate – by transport and rigorous electromagnetic simulations – that light-trapping enhanced thin-film cells with twenty InAs/GaAs QD layers reach efficiency higher than 28% under unconcentrated light, ambient temperature. If photon recycling can be fully exploited, 30% efficiency is deemed to be feasible.

    更新日期:2018-01-03
  • InAs thermophotovoltaic cells with high quantum efficiency for waste heat recovery applications below 1000 °C
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-12-29
    Qi Lu, Xinxin Zhou, Andrey Krysa, Andrew Marshall, Peter Carrington, Chee-Hing Tan, Anthony Krier

    InAs thermophotovoltaic (TPV) cells with external quantum efficiency at the peak wavelengths reaching 71% at low temperature and 55% at room temperature are reported, which are the highest values to date for InAs. The TPV exhibited 10% power conversion efficiency at 100 K cell temperature. The dark and light current-voltage characteristics were measured at different cell temperatures (100–340 K) in response to heat sources in the range 500–800 °C. The resulting dependences of the output voltage and current as well as the spectral response of the InAs TPV have been extensively characterized for waste heat recovery applications. The performance of these cells is strongly determined by the dark current which increases rapidly with increasing cell temperature originating from bandgap narrowing, which resulted in a reduction of open circuit voltage and output power.

    更新日期:2017-12-31
  • Silica fume/capric acid-palmitic acid composite phase change material doped with CNTs for thermal energy storage
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-12-29
    Ahmet Sarı, Alper Bicer, Amir Al-Ahmed, Fahad A. Al-Sulaiman, Md. Hasan Zahir, Shamseldin A. Mohamed
    更新日期:2017-12-31
  • Surface and bulk effects of K in Cu1−xKxIn1−yGaySe2 solar cells
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-12-29
    Christopher P. Muzzillo, Timothy J. Anderson
    更新日期:2017-12-31
  • Broadband spectral response of diamond wire sawn mc-Si solar cell with omnidirectional performance and improved appearance
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-12-29
    Y.F. Zhuang, S.H. Zhong, H.Y. Xu, W.Z. Shen

    Highly efficient diamond wire sawn (DWS) multi-crystalline Si (mc-Si) solar cells with a satisfactory visual appearance are expecting to dominate the photovoltaic industry soon. Here, we report the realization of broadband spectral response of DWS mc-Si solar cells with omnidirectional performance and improved appearance. The success lies in the effective surface texturization based on MACE technique followed by post acid modification and the introduction of SiO2/SiNx stack layers on the rear side. Bowl-like pits with an open size of about 1 µm are uniformly formed on the Si surface regardless of the crystallographic directions, which significantly enhances the antireflection ability in the short wavelength and makes the grain boundaries less noticeable. We have also shown that the bowl-like textured cells possess exceptional optical absorption over wide angles of incidence from 0° to 70°. Moreover, the SiO2/SiNx stack layers enhance the rear internal reflection and passivation, effectively increasing the long wavelength absorption and suppressing the electrical losses. We have successfully mass-produced DWS mc-Si solar cells with an average efficiency of 19.1%, which is 1.2% absolutely higher than that of the conventional micro-textured counterparts.

    更新日期:2017-12-31
  • Investigating coating method induced vertical phase distribution in polymer-fullerene organic solar cells
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-12-27
    C.Y. Jiang, V. Chellappan, W.P. Goh, J. Zhang

    The morphologies of bulk heterojunction (BHJ) films of blended semiconductor of poly(3-hexylthiophene) (P3HT) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61 (PCBM) deposited by doctor blading and spin coating were investigated. Controlled phase separation in BHJ organic/polymer solar cells (OSCs) were achieved using doctor blading. The results revealed that the coating method induced a significant difference in the film morphology. The vertical phase distribution of the BHJ layer fabricated by doctor blading was uniform, while uneven phase distribution was observed in spin coated BHJ layer. The uniform phase distribution in the doctor blading coated film resulted in higher charge carrier mobility and power conversion efficiency in solar cell than those in films fabricated from spin coating. The results demonstrated that doctor blading has advantages not only in large area high throughput and roll-to-roll compatibility, but also in better control of film morphology to achieve high efficiency consistently in OSC devices.

    更新日期:2017-12-27
  • Ultra-broadband perfect solar absorber by an ultra-thin refractory titanium nitride meta-surface
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-12-27
    Zhengqi Liu, Guiqiang Liu, Zhenping Huang, Xiaoshan Liu, Guolan Fu

    Electromagnetic wave absorbers with thinner structural thickness but with broader spectral absorption bandwidth are more desirable for various applications in solar energy and optoelectronics. In this work, a refractory titanium nitride meta-surface with efficient, ultra-broadband solar energy absorption is theoretically designed and numerically demonstrated. The resulting 250-nm-thick meta-surface absorber exhibits an ultra-broadband perfect absorption over the whole ultraviolet-visible-near infrared range. With taking the A > 90% into account, the absorption bandwidth is up to 1110 nm with the wavelength range varied from 0.316 μm to 1.426 μm. The titanium nitride nano-resonators array and its coating structure of titanium dioxide array cooperatively provide multiple resonant modes, which therefore introduce strong coupling with the solar radiation and eventually produce an ultra-broadband absorption. The absorption spectrum can be feasibly manipulated via tuning the structural parameters. Most importantly, in sharp contrast to the common absorbers formed with metallic nano-resonators, the titanium nitride based solar absorber is with much stronger thermal stability, illustrating the impressive promise for wide applications such as thermo-photovoltaics and other high-power optoelectronic processes.

    更新日期:2017-12-27
  • Thickness dependent surface roughness of sputtered Li2.5TaOx ion conductor and its effect on electro-optical performance of inorganic monolithic electrochromic device
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-12-26
    Yu Xiao, Guobo Dong, Junji Guo, Qirong Liu, Qingjiao Huang, Qianqian Zhang, Xiaolan Zhong, Xungang Diao

    Transparent amorphous Li2.5TaOx thin films with different thicknesses were deposited by RF magnetron sputtering. The ionic conductivities of as-deposited films determined by ac impedance spectroscopy were of the order of 10−8 S/cm at room temperature. The surface roughness increased rapidly with the film thickness increasing as confirmed by scanning electron microscopy and atomic force microscopy. Inorganic monolithic electrochromic devices (ECDs) based on WO3//NiO complementary structure were fabricated using the Li2.5TaOx with different thicknesses as the ion conductor layers. The electro-optical performance of the ECDs was characterized by cyclic voltammetry and chronoamperometry. The ECDs showed a highest optical modulation of 40% at 550 nm driven by − 1.5 V (coloration) and 1 V (bleaching) with switching time of 30 s. Both the amount of transferred charge and coloration efficiency were found to be highly dependent on the film thickness of Li2.5TaOx layer. The high charge transfer resistance at the Li2.5TaOx/WO3 interface and poor growth of WO3 layer due to the high surface roughness of Li2.5TaOx may well account for the decreased device performance.

    更新日期:2017-12-27
  • Properties of glycerol and ethylene glycol mixture based SiO2-CuO/C hybrid nanofluid for enhanced solar energy transport
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-12-26
    Suleiman Akilu, Aklilu Tesfamichael Baheta, Mior Azman M.Said, Alina Adriana Minea, K.V. Sharma
    更新日期:2017-12-27
  • Measurement of dust sweeping force for cleaning solar panels
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-12-24
    Eugene Yu-Ta Chen, Lian Ma, Yuan Yue, Bing Guo, Hong Liang

    A new methodology has been developed to evaluate cleaning efficiency of dust particles on solar panels. Those particles have an average diameter of 2.3 µm and were collected in Doha, Qatar. A brush-disk configuration was constructed to measure the sweeping force as a polymeric tip sliding through a dusted glass substrate. The sweeping force was measured under various applied loads on samples treated in environment of various humidity. Experimental results showed that the cleaning efficiency of dry dust particles was independent of the applied load, reaching higher than 90%. However, the adsorption of water molecules showed pronounced effects on the cleaning efficiency. In order to increase the efficiency in humid environment, the applied load thus needed to be increased. The higher the applied load, the higher the sweeping force, the higher the cleaning efficiency, indicating more power is needed to clean the surface. This research presented an alternative approach to evaluate the cleaning efficiency of dust particles.

    更新日期:2017-12-27
  • Tuning orientation of doped hematite photoanodes for enhanced photoelectrochemical water oxidation
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-12-24
    Song Li, Jiajia Cai, Yinglei Liu, Meiqi Gao, Feng Cao, Gaowu Qin
    更新日期:2017-12-27
  • 更新日期:2017-12-27
  • Partially shaded III-V concentrator solar cell performance
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-12-23
    L.A.A. Bunthof, S. Veelenturf, E.J. Haverkamp, W.H.M. Corbeek, D. van der Woude, G.J. Bauhuis, P. Mulder, E. Vlieg, J.J. Schermer

    Currently, an important concern in CPV is inhomogeneity of the light distribution on the cell introduced by the applied optical systems, which may affect system performance. In BICPV applications, the inhomogeneities can be much more severe because of design constraints introduced by the building incorporation. Additionally, one of the predominant loss mechanisms in CPV solar cells is perimeter recombination. In this study, the electrical parameters of CPV cells are investigated under inhomogeneous illumination intensity profiles. Partial shading is used as a model for extremely inhomogeneous illumination, while several shadow patterns are used to study the effect of perimeter recombination on the cell performance. As the latter occurs most strongly in GaAs subcells, shallow and deep junction GaAs CPV cells have been developed and subjected to these experiments, as well as commercial triple junction CPV cells. Deep junction GaAs cells are shown to perform significantly better under concentrated light than their shallow junction counterparts. A large degree of shading exceeding 70% has been found to cause only minor losses in the cell performance of 4%. Also, the cell performance is found to be independent of the location of illumination, in spite of perimeter recombination effects, because the current density spreads out. Clearly, increased illumination inhomogeneities caused by elaborate BICPV optical systems, do not inhibit the electrical performance strongly. As a consequence, a large degree of design freedom exists for the optical systems, which offers good opportunities to develop BICPV that meet all the design challenges of the built environment.

    更新日期:2017-12-27
  • CdTe thin film solar cells with a SnTe buffer layer in back contact
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-12-23
    Zeping Weng, Songsong Ma, He Zhu, Zhenyu Ye, Tianyu Shu, Jie Zhou, Xuanzhi Wu, Huizhen Wu
    更新日期:2017-12-27
  • Multicrystalline silicon assisted by polycrystalline silicon slabs as seeds
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-12-23
    Chunlai Huang, Huali Zhang, Shuai Yuan, Yihua Wu, Xinhao Zhang, Da You, Lei Wang, Xuegong Yu, Yuepeng Wan, Deren Yang

    An effective method of using polycrystalline silicon (poly-Si) planar slabs as seed materials for industrial low-cost and high-quality seed-assisted multicrystalline silicon has been presented. The interspace volume of the poly-Si slab seed layer is much lower compared to poly-Si nugget seed layer, so the initial grains of the slab-assisted ingot are much more uniform than those of the nugget-assisted ingot. Photoluminescence (PL) and minority lifetime measurements showed a considerable reduction in dislocation cluster density in the slab-assisted ingot, especially at the middle and top regions. The average cell efficiency based on the slab-assisted ingot is enhanced by 0.12% in absolute value compared to the nugget-assisted ingot. Moreover, the bottom edge of slab-assisted ingot can be fully recycled through existing cleaning process without remaining SiC particles, which saves considerable materials and slicing costs in mass manufacturing compared to nugget-assisted growth method.

    更新日期:2017-12-27
  • Synthesis and optoelectrochemical properties of a magenta-to-transmissive electrochromic polymer based on 3, 4-dioxythiophene
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-12-23
    Xiaoming Chen, Qishu Qu

    A new magenta-to-transmissive electrochromic polymer, poly(3,4-bis(3-bromopropoxy)thiophene) (PBBrPOT) was synthesized by electrochemical polymerization and its electrochromic properties were characterized in detail. Compared with the representative “large-volume alkyl substituents” strategy, herein we use bromines as the end-capping groups of two propoxyl substituents on the 3- and 4- position of the thiophene ring to introduce more steric repulsion within the polymer chains, and therefore obtain a magenta neutral state of the polymer. The PBBrPOT film shows a set of reasonable electrochromic features, including low driving potentials (−0.1 V and 0.9 V), appropriate transmittance change (38% at 556 nm), but a relatively longer response time in bleaching process (t95 = 6.5 s).

    更新日期:2017-12-27
  • 更新日期:2017-12-22
  • 更新日期:2017-12-22
  • Light-induced current mapping in oxide based solar cells with nanoscale resolution
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-12-21
    Shrabani Panigrahi, Tomás Calmeiro, Rodrigo Martins, Elvira Fortunato
    更新日期:2017-12-21
  • Solid state ITO|Au-NPs|TiO2 plasmonic based solar cells
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-12-21
    Adam Ginsburg, Maayan Priel, Hannah Noa Barad, David A. Keller, Elana Borvick, Kevin Rietwyk, Adi Kama, Simcha Meir, Assaf Y. Anderson, Arie Zaban

    Plasmonic enhanced solar cells are widely studied due to their increased performance arising from the metallic nanoparticles light absorption and scattering. In contrast, there are only few reports on solar cells which are based solely on the plasmonic metallic layer as the absorber. These cells are operating by hot electron injection in a Schottky barrier formed between the metallic nanoparticles and a semiconductor. In this work, we present photovoltaic cells which are based on an ultra-thin tunable Au layer as the only light absorbing material. These cells are in the solid state configuration composed of ITO|Au NP's|TiO2. High throughput methods are used in order to optimize the performance, which reaches 1 mA cm−2 of current, and a voltage of 100 mV under one sun illumination. The incident photon to electron conversion efficiency is 5.84% at 700 nm, the highest reported for a solid-state device so far. These cells are the first step towards a plasmonic based tandem cell.

    更新日期:2017-12-21
  • Effective impurity gettering by phosphorus- and boron-diffused polysilicon passivating contacts for silicon solar cells
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-12-21
    AnYao Liu, Di Yan, Sieu Pheng Phang, Andres Cuevas, Daniel Macdonald

    This paper presents direct experimental evidence for the strong impurity gettering effects associated with the formation of both phosphorus and boron doped polysilicon/oxide passivating contacts for silicon solar cells, doped via thermal diffusion from POCl3 or BBr3 sources. Ion-implanted iron is used as a marker to quantify the gettering effectiveness via carrier lifetime measurements. The process conditions for fabricating optimum polysilicon passivating contacts are found to remove more than 99.9% of the iron from the silicon wafer bulk. The gettering effects of POCl3 and BBr3 diffused polysilicon/oxide contacts mainly arise from the dopant diffusions, as opposed to gettering by structural defects in the polysilicon films. The thin oxide interlayer hinders the gettering effectiveness at low diffusion temperatures, although its blocking effect becomes small at the moderate temperatures used to fabricate optimum polysilicon contacts. The gettering effectiveness increases with increasing diffusion temperature. The gettering of iron from the silicon wafer bulk to the surface layers is found to have a negligible impact on their ability to suppress recombination at the interface with the silicon wafer. Therefore, the formation of polysilicon/oxide passivating contacts, via thermal diffusion from POCl3 and BBr3 sources, not only achieves high quality surface and contact passivation but also has the net additional benefit of achieving very effective gettering of unwanted impurities in the silicon wafer bulk.

    更新日期:2017-12-21
  • 更新日期:2017-12-19
  • Automated design of multi junction solar cells by genetic approach: Reaching the >50% > 50 % efficiency target
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-12-13
    Slobodan Čičić, Stanko Tomić

    The proper design of the multi-junction solar cell (MJSC) requires the optimisation search through the vast parameter space, with parameters for the proper operation quite often being constrained, like the current matching throughout the cell. Due to high complexity number of MJSC device parameters might be huge, which makes it a demanding task for the most of the optimising strategies based on gradient algorithm. One way to overcome those difficulties is to employ the global optimisation algorithms based on the stochastic search. We present the procedure for the design of MJSC based on the heuristic method, the genetic algorithm , taking into account physical parameters of the solar cell as well as various relevant radiative and non-radiative losses. In the presented model, the number of optimising parameters is View the MathML source 5 M + 1 for a series constrained M -junctions solar cell. Diffusion dark current, radiative and Auger recombinations are taken into account with actual ASTM G173-03 Global tilted solar spectra, while the absorption properties of individual SCs were calculated using the multi band k·p k · p Hamiltonian. We predicted the efficiencies in case of M=4 M = 4 to be 50.8% 50.8 % and 55.2% 55.2 % when all losses are taken into account and with only radiative recombination, respectively.

    更新日期:2017-12-15
  • Challenges and strategies for implementing the vertical epitaxial heterostructure architechture (VEHSA) design for concentrated photovoltaic applications
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-12-12
    Mark C.A. York, Antoine Mailhot, Abderraouf Boucherif, Richard Arès, Vincent Aimez, Simon Fafard

    Monochromatic conversion efficiencies in excess of 60% have been achieved with Vertical Epitaxial HeteroStructure Architechture laser power converters (with anywhere from 5 to 20+ n/p junctions stacked vertically). We are presently investigating the applicability of this design to solar cells, whereby the individual junctions of a multi-junction cell are replaced with a current matched stack of subcells. If viable, such a design offers the potential for efficiency gains via reduced I2R I 2 R losses and elevated Voc V oc . Moreover, splitting the short-circuit current over additional junctions opens up the possibility of operation under concentration ratios otherwise considered impractical for conventional cells.

    更新日期:2017-12-15
  • Work function optimization of vacuum free top-electrode by PEDOT:PSS/PEI interaction for efficient semi-transparent perovskite solar cells
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-12-11
    Kang Min Kim, Sunyong Ahn, Woongsik Jang, Soyun Park, O Ok Park, Dong Hwan Wang
    更新日期:2017-12-15
  • Electrochromism of hexagonal sodium tungsten bronze nanorods
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-12-08
    Tao Gao, Bjørn Petter Jelle

    Single-crystalline sodium tungsten bronze (Na-WO3) nanorods with typical diameters of 10–200 nm and lengths of several microns have been prepared via a simple hydrothermal method. The as-prepared Na-WO3 nanorods crystallize in a hexagonal structure and elongate along the <001> crystallographic direction. The as-prepared Na-WO3 nanorods have eight diagnostic Fourier transform infrared (FTIR) absorptions at 3604, 3545, 1622, 1600, 983, 790, 480 and 430 cm−1, which represent specific fingerprints of the vibrational features of hexagonally tunnel-structured Na-WO3 containing tunnel water molecules. The as-prepared Na-WO3 nanorods exhibit a typical cathodic electrochromism, which is related to a proton-electron double insertion process. X-ray diffraction results indicate a phase transformation of hexagonal Na-WO3 nanorods during the electrochromic process, of which the involved local structural evolutions such as water decomposition and proton insertion have been discussed by using FTIR spectroscopy. The results suggest that, during the electrochromic coloration process, the inserted protons might occupy the small trigonal tunnel positions instead of the large hexagonal ones.

    更新日期:2017-12-15
  • Relative impacts of methylammonium lead triiodide perovskite solar cells based on life cycle assessment
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-11-22
    Jaume-Adrià Alberola-Borràs, Rosario Vidal, Emilio J. Juárez-Pérez, Elena Mas-Marzá, Antonio Guerrero, Iván Mora-Seró

    The environmental performance of four different device assembly procedures based on hybrid halide perovskite solar cell (PSC) were assessed from cradle to grave using life cycle assessment (LCA) methodology. In addition, a new environmental indicator was defined to measure the time evolution of an impact category, specifically in this case, human toxicity cancer payback time. PSCs procedures accounted for the probably three more used basic recipes for laboratory perovskite deposition: 1) spin coating of stoichiometric precursor solution, 2) spin coating of precursor solution using lead chloride precursor and 3) the two step deposition method. Also, the two most widely used substrate configurations (planar and mesoporous substrate)were considered. LCA included three realistic scenarios for the end of life: 1) residual landfill, 2) reuse and residual landfill and 3) reuse and recycling. The remaining variable parameters to assemble the device were fixed in common for all four devices, which were the major responsible of the whole PSC impact. Lead of PSCs had no significant contribution in environmental impacts. Beyond shared procedure steps, impacts generated by the two-step method and the use of mesostructured type substrate were higher. End of life scenario with reuse and recycling improved the toxicity impact categories.

    更新日期:2017-12-15
  • On the use of metal cation-exchanged zeolites in sorption thermochemical storage: Some practical aspects in reference to the mechanism of water vapor adsorption
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-11-22
    Delhia Alby, Fabrice Salles, Julien Fullenwarth, Jerzy Zajac

    The sodium form of industrial X-zeolite (13X) was compared with two other samples obtained by a partial (about 70%) cation exchange with Mg2+ (Mg-X) or a complete exchange with Ca2+ (Ca-X) in view of their use as adsorbents for water vapor in energy storage systems by sorption. Various sorption methods based on the specific interactions between two probing molecules (N2 and NH3) and specific surface sites were employed to monitor the hydration state of the zeolite surface as a function of the temperature of sample drying performed under vacuum degassing or gas-flow conditions. X-ray diffraction, volumetric sorption technique, temperature-programmed desorption, and gas flow calorimetry were combined with Monte Carlo simulations of the mechanism of water vapor adsorption on model zeolites to demonstrate that the general tendency to operate under mild drying conditions would always result in a state of partial hydration of the zeolite surface. To increase the amount of heat released upon subsequent adsorption from a flow of helium at a relative pressure of water vapor of about 0.03, the use of Mg-X sample was demonstrated the best alternative if the activation procedure was to be performed at 200 °C. Here, the heat effect was 4–5 times greater than that measured in the case of 13X. This result is of high importance for the industrial-scale implementation of the energy storage by sorption.

    更新日期:2017-12-15
  • Sebacic acid/CNT sponge phase change material with excellent thermal conductivity and photo-thermal performance
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-11-22
    Qi Zhang, Jian Liu

    Latent heat thermal energy storage system using phase change materials was widely used in solar thermal systems. Here, a novel form-stable phase change composite was successfully prepared. The sebacic acid is encapsulated by carbon nanotube sponge. The as-prepared composite is determined by SEM, FT-IR and XRD and the results show that the paraffin is mostly encapsulated in the pores of carbon nanotube sponge. The DSC measurements indicate that the melting temperature and latent heat of the composite are 121.1 °C and 131.8 J g−1, respectively. The phase change composite could maintain its phase transition perfectly after 200 melting−freezing cycles, and no leakage of sebacic acid was observed by further SEM observation. The as-prepared composite shows 27-fold thermal conductivity enhancement as compared to the pure sebacic acid. Further, the as-prepared composite shows great photo-thermal performance when under simulated solar irradiation. Hence, the carbon nanotube sponge based high temperature phase change composite has great potential in solar thermal application.

    更新日期:2017-12-15
  • A practical wave-optical hemispheroidal nanostructure strategy for photonic-enhanced thin film solar cells
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-11-21
    Qian Huang, Xiaoyuan Lin, Yupeng Tong, Jian Ni, Li Zhang, Xiaonan Lu, Ying Zhao, Xiaodan Zhang

    The interaction between light and wavelength-sized photonic nanostructure is highly promising for light management applied to thin-film photovoltaics (PVs). In this work, we put forward a practical wave-optical dielectric hemispheroidal nanostructure strategy under cost-effective anodic oxidation approach and substrate transfer method. By adjusting the oxidation voltage, periodic hemispheroidal nanostructure with diametral scale over 650 nm was obtained. Due to their wavelength-scale dimension, enhanced diffraction behavior and guided resonance were identified through finite-difference-time-domain (FDTD) simulation resulting in significant forward-scattering capabilities. The coherent optical performance was investigated experimentally and theoretically. To leverage the benefits of hemispheroidal nanostructure, amorphous silicon absorb layer and solar cell were fabricated. Compared with the planer structure, the developed hemispheroidal nanostructure could significantly improve the absorption of a-Si:H layer via light management with a 10.97% enhancement in the overall external quantum efficiency. Effective improvements in Voc and FF performances were also obtained in comparison to an etched AZO structure with high surface roughness. As the first demonstration, it was found that the hemispheroidal nanostructure by coating on the surface of a-Si:H thin film solar cells led to 7.79% and 7.38% enhancements respectively in overall energy conversion efficiency in comparison to the planar and the etched AZO structure.

    更新日期:2017-12-15
  • Corrosion of steel alloys in molten NaCl + Na2SO4 at 700 °C for thermal energy storage
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-11-21
    Madjid Sarvghad, Geoffrey Will, Theodore A. Steinberg

    Stainless steel 316, duplex steel 2205 and carbon steel 1008 were examined for compatibility with the eutectic mixture of NaCl + Na2SO4 at 700 °C in air for thermal energy storage. Electrochemical measurements combined with advanced microscopy techniques were employed. Results confirmed oxidation to be the primary attack to all metals. Ferritic alloy 1008 was found the most vulnerable alloy with severe oxidative attack. Alloys 316 and 2205 showed close performance while grain boundary oxidative and sulfur attack threatened these materials. Alloy 2205 showed chromium depletion followed by selective oxidation of ferrite in the presence of a semi-protective film on the surface.

    更新日期:2017-12-15
  • Boron subphthalocyanines as electron donors in outdoor lifetime monitored organic photovoltaic cells
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-11-20
    Richard K. Garner, David S. Josey, Stephanie R. Nyikos, Aleksa Dovijarski, Jon M. Wang, Greg J. Evans, Timothy P. Bender

    Structural variants of boron subphthalocyanines were tested as light absorbing and electron donating materials paired with C60 in organic photovoltaic cells, in a rooftop ambient environment according to ISOS-O3 protocols. Constant current monitoring and daily current-voltage sweeps, reinforced by irradiance and temperature tracking, reveal differing degradation rates depending on the chemical structure of the boron subphthalocyanine. Results suggest that the observed initial burn-in efficiency loss observed in all devices is due to C60, but that the longer term degradation trend is attributable to the chemical breakdown of the subphthalocyanine donors through hydrolysis. These findings demonstrate that the molecular structure of boron subphthalocyanines is a significant handle on device longevity, and that a structure-property relationship can be established for stability. The results also highlight the need for alternative electron accepting materials to C60 for pairing with boron subphthalocyanines in planar heterojunction solar cells, as well as the necessity of a more robust encapsulation methodology.

    更新日期:2017-12-15
  • Eutectic composition-dependence of latent heat of binary carbonates (Na2CO3/Li2CO3)
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-11-20
    Zhiwei Ge, Yun Huang, Yulong Ding

    Phase change materials (PCMs) are promising alternative candidates for a variety of thermal energy storage and related applications. Among the PCMs, alkali carbonates have received particular attention in recent years due to their favourable thermophysical properties at high temperatures. However, the use of such carbonates as PCM requires the understanding of the structural information of the material particularly at both the solid and molten states and the composition dependence of the latent heat, which are largely lacking. Here we study, by both experiments and molecular dynamics simulations, the latent heat of the binary carbonates Na2CO3/Li2CO3. The results show that the binary carbonates can convert to LiNaCO3 within a wide concentration range. A eutectic composition (EC) region of about 51 mol. % Li2CO3 has shown the largest conversion to the LiNaCO3. Any excess loading of Na2CO3 or Li2CO3 beyond the EC region of the carbonates could lower the activation energy of diffusion. The solidification of the carbonates leads to a higher phase change resistance in the EC region with a higher activation energy Ea(pc) and a larger latent heat during the phase change.

    更新日期:2017-12-15
  • ZnO-Au composite hierarchical particles dispersed oil-based nanofluids for direct absorption solar collectors
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-11-20
    Xinzhi Wang, Yurong He, Meijie Chen, Yanwei Hu

    Direct absorption solar collector (DASC) is a promising technology for solar energy harvesting. Recently, nanofluids have shown great potential for DASC applications due to their tunable optical absorption properties. An advanced composite combining plasmonic gold nanoparticles (Au NPs) and hedgehog-like hierarchically structured ZnO particles (HPs) was prepared and used in DASCs. The nanofluid prepared with 1.0 mg mL−1 HP-Au exhibited excellent stability and broadband optical absorption properties, and reached an equilibrium temperature of ~125 °C within 1 h of solar heating at an irradiation power of 10 kW m−2. A new photothermal conversion efficiency model was established to evaluate the solar harvesting performance of the HP-Au/oil nanofluid by simultaneously considering the effect of the working fluid temperature on the heating and cooling efficiencies. Compared to the base fluid, the HP-Au/oil nanofluid exhibits a 240% enhancement in photothermal conversion efficiency. The HP-Au/oil nanofluid shows great potential as a working fluid in direct absorption solar collectors.

    更新日期:2017-12-15
  • Influence of MgCl2 content on corrosion behavior of GH1140 in molten NaCl-MgCl2 as thermal storage medium
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-11-20
    Jun-wei Wang, Hong-xia Zhou, Cui-zhen Zhang, Wen-ning Liu, Bai-yao Zhao

    As a thermal energy storage medium (TESM) at moderate-high temperature of concentrating solar power (CSP), the molten NaCl-MgCl2 has sharp corrosive action on a metal container. The influence of MgCl2 content on a metal corrosion behavior is not clear. The corrosion behavior of a Fe based alloy (GH1140) in molten NaCl-MgCl2 (at 1123 K) with different content of MgCl2 (wt%:0.0,48.9,61.0,93.6) were studied by the submergence corrosion experience. Results show that: after corrosion for 5 h, there is a negative correlation between the weight loss of samples and the content of MgCl2. In the molten salt without MgCl2, the sample was corroded according to the mechanism of “dissolution as anode- oxidizing- peeling off of oxide film”. After adding a little MgCl2 in the molten salt, an unprotected MgO shell was formed on the sample surface. The samples weight decreased and obeyed a line law. The elements of Fe and Cr deplete in the corrosion layer. Corrosion mechanism is “dissolution as anode- oxidizing- reduction- chlorination”. When the content of MgCl2 is very high in the molten salt, partial pressure of Cl2 increases. The corrosion mechanism is similar to what in the molten salt with a little MgCl2, but the chlorination reaction is more severe.

    更新日期:2017-12-15
  • Degradation of multijunction photovoltaic gridlines induced via thermal cycling
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-11-20
    Ryan E. Brock, Peter Hebert, James Ermer, Reinhold H. Dauskardt

    A well-known but heretofore uncharacterized failure mechanism in multijunction photovoltaic cells involves the development of cracks in the top cell directly adjacent to metal gridline structures. In this study, we systematically explore the potential evolution of stress, grain size, roughness, and hardness of metal gridlines during thermal cycling as it pertains to top cell cracking behavior. We discover that although top cells are found to crack after many cycles, this is not due to an accumulation of stress or damage, but rather a progression of strain hardening within the metal gridlines due to cyclic plastic deformations, quantified as an increase in hardness of as much as 57%. Furthermore, optical and topological characterization reveals morphology changes at the gridlines’ top surfaces, lending some insight to commonly observed bus bar wire-bonding issues. Ultimately this suite of characterization techniques not only reveals the underlying behavior leading to gridline-induced top cell cracking failures in multijunction photovoltaics, but also suggests a route forward for the development of improved gridline materials.

    更新日期:2017-12-15
  • Characterization of medium-temperature phase change materials for solar thermal energy storage using temperature history method
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-11-16
    Zhaowen Huang, Ning Xie, Zigeng Luo, Xuenong Gao, Xiaoming Fang, Yutang Fang, Zhengguo Zhang

    In this work, thermal properties of five phase change materials (PCMs) with medium phase change temperature including mannitol, sebacic acid (SA), SA/expanded graphite (EG) composite, LiNO3-KCl eutectic salt and LiNO3-KCl/EG composite, were characterized using temperature history (T-history) method with improved accuracy. The studies on mannitol showed that although the T-history method could yield a supercooling degree which was lower than that from differential scanning calorimetry (DSC) determination, the severe supercooling and great latent heat loss during mannitol's solidification were still the problems which hindered the use of this material. As for the rest materials, slight or no supercooling phenomena were observed and the obtained phase change temperatures were well matched to literature data. The latent heat measurements of these four materials proved a proportional relationship between the PCM/EG composite's latent heat and PCM's mass fraction. However, the latent heat values determined by T-history were higher than the DSC results. Therefore, repeated studies were still required to further evaluate the latent heat storage densities of these materials. The results in this work could play key roles in design, simulation and modification of latent thermal energy storage (LTES) systems based on these medium-temperature PCMs for solar heat applications.

    更新日期:2017-12-15
  • Up-scalable sheet-to-sheet production of high efficiency perovskite module and solar cells on 6-in. substrate using slot die coating
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-11-16
    Francesco Di Giacomo, Santhosh Shanmugam, Henri Fledderus, Bardo J. Bruijnaers, Wiljan J.H. Verhees, Maarten S. Dorenkamper, Sjoerd C. Veenstra, Weiming Qiu, Robert Gehlhaar, Tamara Merckx, Tom Aernouts, Ronn Andriessen, Yulia Galagan

    Scalable sheet-to-sheet slot die coating processes have been demonstrated for perovskite solar cells and modules. The processes have been developed on 6 in. × 6 in. glass/ITO substrates for two functional layers: the perovskite photo-active layer and the Spiro-OMeTAD hole transport layer. Perovskite solar cells produced using these slot die coating processes demonstrate device performances identical to the spin coated devices. All manufactured devices illustrate a high level of reproducibility. The developed slot die coating processes were also used for the manufacturing of perovskite PV modules. Large area modules of 12.5 × 13.5 cm2 were realized by slot die coating on 6 in. × 6 in. substrates in combination with newly developed laser ablation processes for conventional P1-P2-P3 monolithic cell interconnections. The modules demonstrate power conversion efficiencies above 10%, with a power output of 1.7 W. This achievement is an important milestone in the development of up-scalable manufacturing technologies for perovskite PV modules.

    更新日期:2017-12-15
  • Printable liquid silicon for local doping of solar cells
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-11-16
    Felix Haase, Bianca Lim, Agnes Merkle, Thorsten Dullweber, Rolf Brendel, Christian Günther, Michael H. Holthausen, Christoph Mader, Odo Wunnicke, Robby Peibst

    We demonstrate the application of a liquid-processed doped silicon precursor as a doping source for the fabrication of interdigitated back contact solar cells. We integrate phosphorus- as well as boron-doped liquid silicon in our n-type interdigitated back contact cell process based on laser-structuring. The cell with the phosphorus back surface field from liquid silicon has an efficiency of 20.9% and the cell with the boron emitter from liquid silicon has an efficiency of 21.9%. We measure saturation current densities of 34 fA cm−2 on phosphorus-doped layers with a sheet resistance of 108 Ω/sq and 18 fA cm−2 on boron-doped layers with a sheet resistance of 140 Ω/sq using passivated test samples.

    更新日期:2017-12-15
  • On the origin of band-tails in kesterite
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-11-14
    G. Rey, G. Larramona, S. Bourdais, C. Choné, B. Delatouche, A. Jacob, G. Dennler, S. Siebentritt

    Kesterite Cu2ZnSn( S x Se 1 − x )4 is an attractive earth-abundant material for low-cost thin film photovoltaics with the capability to achieve power production in the terawatt range and therefore to supply a significant part of the global electricity needs. Despite its advantageous optical and electrical properties for photovoltaic applications, the large band tailing causes voltage losses that limit the efficiency of kesterite-based devices. Here we show that the band-tailing originates mainly from band-gap fluctuations attributable to chemical composition variations at nanoscale; while electrostatic fluctuations play a lesser role. Absorption measurement reveal that the Cu-Zn disorder, always present in kesterite Cu2ZnSn( S x Se 1 − x )4, is not the main source of the large band tailing. Instead defect clusters having a significant impact on the band-edge energies, e.g. [2 Cu Zn − + Sn Zn 2 + ], are proposed as the main origin for the kesterite band tail.

    更新日期:2017-12-15
  • Development of low-cost inorganic salt hydrate as a thermochemical energy storage material
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-11-14
    V. Mamani, A. Gutiérrez, S. Ushak

    Thermochemical storage is based on a reversible chemical reaction; energy can be stored when an endothermic chemical reaction occurs and then, energy is released when it is reversed in an exothermic reaction. According to literature and based on the energy storage density (esd), MgCl2·6H2O is a promising candidate material for thermochemical energy storage. Bischofite is an inorganic salt obtained as a by-product material from extraction processes of non-metallic minerals, from Salar de Atacama in Chile, containing approximately 95% of MgCl2·6H2O. Thus, the purpose of this study was to characterize the dehydration reaction of bischofite ore, studied as a low-cost thermochemical storage material. Thermogravimetric data for bischofite were obtained using a TGA instrument coupled to a DSC, at four different isotherms 70 °C, 80 °C, 90 °C and 100 °C. The results of conversion reaction (α-t) from the thermal dehydration experiments, demonstrated the first phase of dehydration with the loss of two water molecules. The study showed a typical sigmoid curve with a significant acceleration in the conversion at the beginning of the reaction until it reaches a maximum rate, where the curve keeps constant. The same behavior was observed for all the temperatures used. The kinetics of bischofite dehydration model was determined using the isothermal kinetics method. For this, the thermogravimetric data were fitted to the most used kinetic models (D, F, R, A) and then their respective correlation coefficients R were evaluated. The results indicated that the dehydration reaction of bischofite was described by the kinetics of chemical reaction of cylindrical particles R2. The rate of dehydration reaction and esd of bischofite are lower as compared to synthetic MgCl2·6H2O, at temperatures higher than 80 °C. However, the cost of materials to store 1 MJ of energy is three times lower for bischofite, which is an evident advantage to promote the reuse of this material left as waste by the non-metallic industry.

    更新日期:2017-12-15
  • New switchable mirror device with a counter electrode based on reversible electrodeposition
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-11-13
    Seong M. Cho, Sujung Kim, Tae-Youb Kim, Chil Seong Ah, Juhee Song, Sang Hoon Cheon, Joo Yeon Kim, Hojun Ryu, Yong-Hae Kim, Chi-Sun Hwang, Jeong-Ik Lee

    A new structure for a switchable mirror device based on reversible electrodeposition is proposed. This device does not contain Cu ions in the electrolyte and adapts a counter electrode. The feasibility of the device was evaluated with a WO3 film, which is a well-known electrochromic material, as a counter electrode. Even in the absence of Cu ions, the WO3 film facilitates a clean erase feature in the device. Furthermore, using a pre-deposited Ag film as a working electrode, Ag deposition can be driven at a substantially lower voltage than that in conventional devices. Moreover the deposition current decreases with the progress of Ag deposition, and stops after completion of the deposition process. The results clearly indicate that the tri-bromine ion, which makes the self-erasing circulation, is not generated during Ag deposition process. The new switchable mirror shows excellent bistability and size scale-up is possible because it does not consume continuous current in the mirror state. By appling the proposed technology, a switchable mirror device with a 7 cm × 9 cm active area was successfully fabricated.

    更新日期:2017-12-15
  • Facile synthesis of mesoporous VO2 nanocrystals by a cotton-template method and their enhanced thermochromic properties
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-11-08
    Shaowen Wu, Shouqin Tian, Baoshun Liu, Haizheng Tao, Xiujian Zhao, R.G. Palgrave, G. Sankar, I.P. Parkin

    As a very promising thermochromic material, VO2 (M/R) (Monoclinic/Rutile) has not been widely applied in smart windows due to its intrinsic low solar modulation (ΔTsol) and low luminous transmission (Tlum). To address this issue, porous structures have been introduced into the VO2 film. Herein, mesoporous VO2 powders with pore size of about 2–10 nm were synthesized using cotton as template by hydrothermal methods. The pore and crystal size of the synthesized VO2 powders can be reliably controlled by the hydrothermal temperature. The mesoporous VO2 powders were mixed with PVP to prepare the VO2-based nanocomposite films by spin coating. The VO2-based films show a better performance between ΔTsol and Tlum than that appeared in previous reports. Especially, a larger pore size could lead to a higher visible transmittance and a larger crystal size would facilitate the enhancement in the solar modulation. In this sense, the VO2-based film obtained at the hydrothermal temperature of 180 °C exhibits an outstanding thermochromic performance with ΔTsol of 12.9% and Tlum up to 56.0% due to a larger crystal size and pore size. Therefore, this synthetic route shows a potential method for the application of mesoporous VO2 powders for solar control coatings.

    更新日期:2017-12-15
  • Quantitative theoretical and experimental analysis of alloying from screen-printed aluminum pastes on silicon surfaces
    Sol. Energy Mater. Sol. Cells (IF 4.784) Pub Date : 2017-11-08
    Michael Rauer, Christian Schmiga, Markus Glatthaar, Stefan W. Glunz

    In this study, we present detailed theoretical and experimental investigations on full-area alloying from screen-printed aluminum pastes on silicon surfaces for solar cell applications. We introduce a simple analytical model for the description of the alloying process derived from existing models for evaporated Al layers, which we adapt to printed Al pastes. Thereby, we particularly account for the recrystallization of Si within the paste particles, which we refer to as parasitic Si recrystallization. Applying our model, we demonstrate good accordance of calculated with measured eutectic layer thicknesses. We show that the model can be versatilely used to investigate screen-printed Al-alloyed contacts in detail: We demonstrate that the latent heat of the Al paste significantly influences the alloying process. Thus, the effective peak temperature of the alloying process can be several 100 °C below the set peak temperature of the firing furnace. By combining calculations of the effective peak temperature with measurements of the Al doping concentration, we determine a parameterization of the solid solubility of Al in Si down to the eutectic temperature of 577 °C. Our investigations therefore provide improved understanding of alloying from printed Al pastes and enable the specific optimization of Al-alloyed contacts.

    更新日期:2017-12-15
Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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