Wang, Zhiping - University of Oxford

研究领域

Photovoltaic and Optoelectronic Device Group

近期论文

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Enhanced photovoltage for inverted planar heterojunction perovskite solar cells.Science (New York, N.Y.) 360 (2018) 1442-1446 D Luo, W Yang, Z Wang, A Sadhanala, Q Hu, R Su, R Shivanna, GF Trindade, JF Watts, Z Xu, T Liu, K Chen, F Ye, P Wu, L Zhao, J Wu, Y Tu, Y Zhang, X Yang, W Zhang, RH Friend, Q Gong, HJ Snaith, R Zhu The highest power conversion efficiencies (PCEs) reported for perovskite solar cells (PSCs) with inverted planar structures are still inferior to those of PSCs with regular structures, mainly because of lower open-circuit voltages (Voc). Here we report a strategy to reduce nonradiative recombination for the inverted devices, based on a simple solution-processed secondary growth technique. This approach produces a wider bandgap top layer and a more n-type perovskite film, which mitigates nonradiative recombination, leading to an increase in Voc by up to 100 millivolts. We achieved a high Voc of 1.21 volts without sacrificing photocurrent, corresponding to a voltage deficit of 0.41 volts at a bandgap of 1.62 electron volts. This improvement led to a stabilized power output approaching 21% at the maximum power point. High irradiance performance of metal halide perovskites for concentrator photovoltaicsNATURE ENERGY 3 (2018) 855-861 Z Wang, Q Lin, B Wenger, MG Christoforo, Y-H Lin, MT Klug, MB Johnston, LM Herz, HJ Snaith Controlling Nucleation and Growth of Metal Halide Perovskite Thin Films for High-Efficiency Perovskite Solar Cells.Small (Weinheim an der Bergstrasse, Germany) 13 (2017) N Sakai, Z Wang, VM Burlakov, J Lim, D McMeekin, S Pathak, HJ Snaith Metal halide perovskite thin films can be crystallized via a broad range of solution-based routes. However, the quality of the final films is strongly dependent upon small changes in solution composition and processing parameters. Here, this study demonstrates that a fractional substitution of PbCl2 with PbI2 in the 3CH3 NH3 I:PbCl2 mixed-halide starting solution has a profound influence upon the ensuing thin-film crystallization. The presence of PbI2 in the precursor induces a uniform distribution of regular quadrilateral-shaped CH3 NH3 PbI3 perovskite crystals in as-cast films, which subsequently grow to form pinhole-free perovskite films with highly crystalline domains. With this new formulation of 3CH3 NH3 I:0.98PbCl2 :0.02PbI2 , this study achieves a 19.1% current-voltage measured power conversion efficiency and a 17.2% stabilized power output in regular planar heterojunction solar cells. A generic interface to reduce the efficiency-stability-cost gap of perovskite solar cells.Science (New York, N.Y.) 358 (2017) 1192-1197 Y Hou, X Du, S Scheiner, DP McMeekin, Z Wang, N Li, MS Killian, H Chen, M Richter, I Levchuk, N Schrenker, E Spiecker, T Stubhan, NA Luechinger, A Hirsch, P Schmuki, H-P Steinrück, RH Fink, M Halik, HJ Snaith, CJ Brabec A major bottleneck delaying the further commercialization of thin-film solar cells based on hybrid organohalide lead perovskites is interface loss in state-of-the-art devices. We present a generic interface architecture that combines solution-processed, reliable, and cost-efficient hole-transporting materials without compromising efficiency, stability, or scalability of perovskite solar cells. Tantalum-doped tungsten oxide (Ta-WO x )/conjugated polymer multilayers offer a surprisingly small interface barrier and form quasi-ohmic contacts universally with various scalable conjugated polymers. In a simple device with regular planar architecture and a self-assembled monolayer, Ta-WO x -doped interface-based perovskite solar cells achieve maximum efficiencies of 21.2% and offer more than 1000 hours of light stability. By eliminating additional ionic dopants, these findings open up the entire class of organics as scalable hole-transporting materials for perovskite solar cells. Crystallization Kinetics and Morphology Control of Formamidinium-Cesium Mixed-Cation Lead Mixed-Halide Perovskite via Tunability of the Colloidal Precursor Solution.Advanced materials (Deerfield Beach, Fla.) 29 (2017) DP McMeekin, Z Wang, W Rehman, F Pulvirenti, JB Patel, NK Noel, MB Johnston, SR Marder, LM Herz, HJ Snaith The meteoric rise of the field of perovskite solar cells has been fueled by the ease with which a wide range of high-quality materials can be fabricated via simple solution processing methods. However, to date, little effort has been devoted to understanding the precursor solutions, and the role of additives such as hydrohalic acids upon film crystallization and final optoelectronic quality. Here, a direct link between the colloids concentration present in the [HC(NH2 )2 ]0.83 Cs0.17 Pb(Br0.2 I0.8 )3 precursor solution and the nucleation and growth stages of the thin film formation is established. Using dynamic light scattering analysis, the dissolution of colloids over a time span triggered by the addition of hydrohalic acids is monitored. These colloids appear to provide nucleation sites for the perovskite crystallization, which critically impacts morphology, crystal quality, and optoelectronic properties. Via 2D X-ray diffraction, highly ordered and textured crystals for films prepared from solutions with lower colloidal concentrations are observed. This increase in material quality allows for a reduction in microstrain along with a twofold increase in charge-carrier mobilities leading to values exceeding 20 cm2 V-1 s-1 . Using a solution with an optimized colloidal concentration, devices that reach current-voltage measured power conversion efficiency of 18.8% and stabilized efficiency of 17.9% are fabricated. Monolithic Wide Band Gap Perovskite/Perovskite Tandem Solar Cells with Organic Recombination Layers JOURNAL OF PHYSICAL CHEMISTRY C 121 (2017) 27256-27262 R Sheng, MT Horantner, Z Wang, Y Jiang, W Zhang, A Agosti, S Huang, X Hao, A Ho-Baillie, M Green, HJ Snaith Reproducible Planar Heterojunction Solar Cells Based on One-Step Solution-Processed Methylammonium Lead Halide Perovskites CHEMISTRY OF MATERIALS 29 (2017) 462-473 S Bai, N Sakai, W Zhang, Z Wang, JT-W Wang, F Gao, HJ Snaith Efficient ambient-air-stable solar cells with 2D-3D heterostructured butylammonium-caesium-formamidinium lead halide perovskites Nature Energy 2 (2017) Z Wang, Q Lin, FP Chmiel, N Sakai, LM Herz, HJ Snaith © 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved. Perovskite solar cells are remarkably efficient; however, they are prone to degradation in water, oxygen and ultraviolet light. Cation engineering in 3D perovskite absorbers has led to reduced degradation. Alternatively, 2D Ruddlesden-Popper layered perovskites exhibit improved stability, but have not delivered efficient solar cells so far. Here, we introduce n-butylammonium cations into a mixed-cation lead mixed-halide FA 0.83 Cs 0.17 Pb(I y Br 1-y ) 3 3D perovskite. We observe the formation of 2D perovskite platelets, interspersed between highly orientated 3D perovskite grains, which suppress non-radiative charge recombination. We investigate the relationship between thin-film composition, crystal alignment and device performance. Solar cells with an optimal butylammonium content exhibit average stabilized power conversion efficiency of 17.5 ± 1.3% with a 1.61-eV-bandgap perovskite and 15.8 ± 0.8% with a 1.72-eV-bandgap perovskite. The stability under simulated sunlight is also enhanced. Cells sustain 80% of their post burn-in' efficiency after 1,000 h in air, and close to 4,000 h when encapsulated. Solution-Processed Cesium Hexabromopalladate(IV), Cs2PdBr6, for Optoelectronic Applications.Journal of the American Chemical Society 139 (2017) 6030-6033 N Sakai, AA Haghighirad, MR Filip, PK Nayak, S Nayak, A Ramadan, Z Wang, F Giustino, HJ Snaith Lead halide perovskites are materials with excellent optoelectronic and photovoltaic properties. However, some hurdles remain prior to commercialization of these materials, such as chemical stability, phase stability, sensitivity to moisture, and potential issues due to the toxicity of lead. Here, we report a new type of lead-free perovskite related compound, Cs2PdBr6. This compound is solution processable, exhibits long-lived photoluminescence, and an optical band gap of 1.6 eV. Density functional theory calculations indicate that this compound has dispersive electronic bands, with electron and hole effective masses of 0.53 and 0.85 me, respectively. In addition, Cs2PdBr6 is resistant to water, in contrast to lead-halide perovskites, indicating excellent prospects for long-term stability. These combined properties demonstrate that Cs2PdBr6 is a promising novel compound for optoelectronic applications. Efficient and Air-Stable Mixed-Cation Lead Mixed-Halide Perovskite Solar Cells with n-Doped Organic Electron Extraction Layers. Advanced materials (Deerfield Beach, Fla.) 29 (2017) Z Wang, DP McMeekin, N Sakai, S van Reenen, K Wojciechowski, JB Patel, MB Johnston, HJ Snaith Air-stable doping of the n-type fullerene layer in an n-i-p planar heterojunction perovskite device is capable of enhancing device efficiency and improving device stability. Employing a (HC(NH2 )2 )0.83 Cs0.17 Pb(I0.6 Br0.4 )3 perovskite as the photoactive layer, glass-glass laminated devices are reported, which sustain 80% of their "post burn-in" efficiency over 3400 h under full sun illumination in ambient conditions. Carbazole-based enamine: Low-cost and efficient hole transporting material for perovskite solar cells NANO ENERGY 32 (2017) 551-557 M Daskeviciene, S Paek, Z Wang, T Malinauskas, G Jokubauskaite, K Rakstys, KT Cho, A Magomedov, V Jankauskas, S Ahmad, HJ Snaith, V Getautis, MK Nazeeruddin Near-Infrared and Short-Wavelength Infrared Photodiodes Based on Dye-Perovskite Composites ADVANCED FUNCTIONAL MATERIALS 27 (2017) ARTN 1702485 Q Lin, Z Wang, M Young, JB Patel, RL Milot, LM Maestro, RR Lunt, HJ Snaith, MB Johnston, LM Herz Room-Temperature Atomic Layer Deposition of Al2 O3 : Impact on Efficiency, Stability and Surface Properties in Perovskite Solar Cells.ChemSusChem 9 (2016) 3401-3406 M Kot, C Das, Z Wang, K Henkel, Z Rouissi, K Wojciechowski, HJ Snaith, D Schmeisser In this work, solar cells with a freshly made CH3 NH3 PbI3 perovskite film showed a power conversion efficiency (PCE) of 15.4 % whereas the one with 50 days aged perovskite film only 6.1 %. However, when the aged perovskite was covered with a layer of Al2 O3 deposited by atomic layer deposition (ALD) at room temperature (RT), the PCE value was clearly enhanced. X-ray photoelectron spectroscopy study showed that the ALD precursors are chemically active only at the perovskite surface and passivate it. Moreover, the RT-ALD-Al2 O3 -covered perovskite films showed enhanced ambient air stability. Identification and Mitigation of a Critical Interfacial Instability in Perovskite Solar Cells Employing Copper Thiocyanate Hole-Transporter ADVANCED MATERIALS INTERFACES 3 (2016) ARTN 1600571 J Liu, SK Pathak, N Sakai, R Sheng, S Bai, Z Wang, HJ Snaith Efficient perovskite solar cells by metal ion doping ENERGY & ENVIRONMENTAL SCIENCE 9 (2016) 2892-2901 JT-W Wang, Z Wang, S Pathak, W Zhang, DW deQuilettes, F Wisnivesky-Rocca-Rivarola, J Huang, PK Nayak, JB Patel, HAM Yusof, Y Vaynzof, R Zhu, I Ramirez, J Zhang, C Ducati, C Grovenor, MB Johnston, DS Ginger, RJ Nicholas, HJ Snaith