Double-layer synergistic optimization by functional black phosphorus quantum dots for high-efficiency and stable planar perovskite solar cells
Graphical Abstract
In this work, a double-layer synergistic optimization strategy is demonstrated through incorporating functional black phosphorus quantum dots (BPQDs) into the SnO2 and perovskite layer. Eventually, the perovskite solar cells (PSCs) with functional BPQDs modification achieve a champion efficiency of 22.85% with ultrahigh open-circuit voltage (VOC) (1.22 V). This work provides a route to design strategies within electron transport layer (ETL) and perovskite bulk to improve the performance of the PSCs.
Introduction
Organic-inorganic hybrid perovskite solar cells (PSCs) have achieved steeply progress within a decade and power conversion efficiency (PCE) has significantly risen from 3.8% to a certified value of 25.5%, positioning them as a promising candidate for new-generation photovoltaic devices [1], [2], [3], [4]. Notably, the planar PSCs employing SnO2 electron transport layer (ETL) have gained tremendous attentions due to the low-temperature, simple, and low-cost processing approaches [5], [6]. Together with the good mobility, deep bandgap as well as suitable conduction band position, SnO2 becomes one of the most widely studied ETL materials in planar PSCs [7], [8]. However, the champion PCE value up to now still shows distances from the theoretical Shockley–Queisser limit efficiency of 33%, indicating a large space for further improving device efficiency [9], [10]. Moreover, the stability of planar PSCs is still a stubborn issue for the long-term application of devices, which seriously hinders their commercialization [11], [12].
As a multilayer device, optimization of the single functional layer or adjustment of the interfacial engineering both have a significant impact on the performance of planar PSCs, especially for PCE and stability [13], [14], [15]. With respect to SnO2 layer, trap states with large density caused by the low-temperature procedure are easy to form in the ETL, which can capture electrons and deteriorate the electrical properties of SnO2 [5], [16]. Without further modification, these trap states eventually lead to loss of short-circuit current density (JSC) and fill factor (FF), even dramatically affect stability of devices [17]. In addition to the optimization of intrinsic nature SnO2, obtaining highly crystalline, large grain size, less defect density perovskite films have been of vital importance for advancement in both efficiency and stability. Unfortunately, owing to the ionic nature of perovskite materials as well as their rapid crystal growth process, both small-sized perovskite grains and large amounts of the defects tend to form in polycrystalline perovskite films [18], [19], [20]. Besides the charge recombination via non-radiative recombination channels and ion migration, these defect sites may also accelerate oxygen/moisture infiltration, which reduces the PCE and stability of the device [21]. Therefore, in order to achieve high-efficiency and stable PSCs in a real way, there is an urgent requirement to develop effective and convenient methods for simultaneously optimizing dual layers and interfaces rather than only simply control of one variable.
Currently, there are mainly two strategies for dual optimization or passivation of PSCs: additive engineering in the layer regions and interfacial engineering between various layers [22], [23], [24]. For this interest and taking into account the complexity of device production, some efforts aiming at enhancing the performance of planar PSCs by simultaneously modifying dual layers or interfaces using one functional material were attempted. For instance, Thomas et al. utilized n-butylammonium iodide (C4H12IN; n-BAI) n-BAI to modify the interfaces between perovskite and neighboring charge transport layers. Such PSCs achieved an improved PCE of 22.60% which showed a 14% enhancement compared to that of the controlled device [25]. Chen et al. demonstrated that introduction of polymer molecule thioctic acid (Poly(TA)) into the ETL-perovskite interfaces and perovskite bulk could enhance the carrier extraction efficiency, the water-resisting and light-resisting abilities of the perovskite film, eventually exhibiting a PCE of 20.4% for MAPbI3-based PSCs with negligible hysteresis [26]. Compared to interfacial engineering, additive engineering has many advantages, such as modulating film crystallization and growth, passivating defects in the bulk and at the interface, tuning interfacial structure [23], [27], [28]. Besides, the additive modification in specific layers also reduces the existence of additional interfaces in comparison with interfacial engineering, which thus eliminates possible interfacial defects and the associated specific charge distributions. However, most of the dual passivation strategies were focused on interfacial engineering [26], [29], [30], and the work in the field of dual additive engineering is still in its infancy. On the other hand, the current works are mainly employed the same materials by simply adjusting the thickness or size when applying in different places [29]. Research on the specific design of the selected functional material toward ETL and the light absorption layer is a missing part in additive engineering.
Herein, we present an intentionally designed dual-layer optimization strategy for achieving efficient and stable PSCs, in which black phosphorus quantum dots (BPQDs) is synchronously incorporated into the SnO2 and perovskite bulk. As a famous two-dimensional (2D) material, BP has drawn huge attention owing to its tunable bandgap (0.3–2 eV) and high carrier mobility (1000 cm2 V−1 s−1) [31], [32]. Notably, when appears in the form of BPQDs, it possesses more impressive and unique electronic and optical properties, owing to the quantum confinement and edge effects [33]. In this case, considering the dramatically different role of each functional layer in PSCs, the pristine BPQDs are introduced in SnO2 ETL, which can effectively fill the electron traps and passivate defects of SnO2. Subsequently, 3-aminopropyltriethoxysilane (APTES) surface-modified BPQDs (BPQDs@APTES) is served as a regulating site to facilitate the perovskite nucleation and crystalline growth, passivate defects and improve moisture-resistance of perovskite film. The density functional theory (DFT) calculations further indicate that introduction of BPQDs@APTES into the perovskite layer can increase the defect formation energies and adsorption energies of O2 and H2O molecules. Benefiting from double-layer synergistic optimization effect of the functional BPQDs, the champion PCE of 22.85% is achieved, which has a remarkable open-circuit voltage (VOC) of 1.22 V. The PCE is increased by 19.5% in comparison to the control PSCs without any BPQDs modification (19.13% with VOC of 1.17 V). Remarkably, the non-encapsulated BPQDs-modified PSCs exhibit excellent stability after 30 days under continuous exposure to both ambient atmosphere (88% of original PCEs retained) and 65 ± 5% relative humidity (62% of original PCEs retained).
Section snippets
Solution preparation
Preparation of the SnO2 solution: the precursor of SnO2 ETL is prepared by mixing SnO2 colloidal dispersion liquid with deionized water (1:1 in volume), and then was continuously stirred for 4 h. For precursor of SnO2:BPQDs ETL, BPQDs solutions with different concentrations (0.15, 0.225, 0.3, 0.45 mg mL−1) were initially obtained by dispersing in H2O. Next, the SnO2 colloidal dispersion liquid is dispersed in the different BPQDs solutions (1:1 in volume) and followed by continuously stirring
Results and discussion
The morphology of obtained BPQDs was characterized through transmission electron microscopy (TEM). As shown in Fig. 1a, the size of BPQDs displays a narrow size distribution from 2 to 8 nm, which has an average diameter of 5 nm. The corresponding high-resolution TEM (HRTEM) image of BPQDs exhibits lattice spacing values of 0.21 and 0.18 nm corresponding to the (020) and (121) crystal planes of the BPQDs, respectively (Fig. 1b) [33], [34]. The chemical composition of BPQDs was investigated via
Conclusion
In summary, we demonstrate a double-layer synergistic optimization strategy through incorporating functional BPQDs into the SnO2 and perovskite layer to improve the efficiency and stability of PSCs. Combining with experimental data and theoretical calculations results, it is shown that the double-layer synergistic effect greatly passivates defects both in the SnO2 and perovskite layers. Moreover, it can additionally improve the crystalline growth and the water-resisting of perovskite film.
CRediT authorship contribution statement
Hongwei Song: Resources, Validation, Supervision, Project administration, Funding acquisition. Yuhong Zhang: Investigation, Formal analysis, Methodology, Writing – original draft. Lin Xu: Conceptualization, Writing – review & editing, Resources, Supervision, Funding acquisition. Yanjie Wu: Methodology, Investigation, Writing – review & editing. Qingqing Zhou: Investigation, Methodology. Zhichong Shi: Writing – review & editing. Xinmeng Zhuang: Writing – review & editing. Bin Liu: Writing –
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
This work was supported by the Key Program of NSFC-Guangdong Joint Funds of China (U1801253), the National Natural Science Foundation of China (Grant Nos. 61874[1–70]049, 61822506, 11874181, 61775080), Natural Science Foundation of Jilin Province the Jilin Province Natural Science Foundation of China (No. 20200801017GH), the Special Project of the Province-University Co-constructing Program of Jilin Province (SXGJXX2017-3).
Yuhong Zhang received her M.S. degree from Jilin Normal University in 2020. Currently she is pursuing her Ph.D. degree under the supervision of Prof. Hongwei Song at College of Electronic Science and Engineering, Jilin University. Her main research direction focus on high-efficiency perovskite solar cells.
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Cited by (0)
Yuhong Zhang received her M.S. degree from Jilin Normal University in 2020. Currently she is pursuing her Ph.D. degree under the supervision of Prof. Hongwei Song at College of Electronic Science and Engineering, Jilin University. Her main research direction focus on high-efficiency perovskite solar cells.
Lin Xu obtained her Ph.D. degree in 2011, from Jilin University. From 2016 to 2017, she worked as a post-doctor in INAC-SyMMES-STEP of CEA Grenoble (France). Currently, she serves as a professor in Jilin University, and has published more than 110 SCI-index papers. Her research area is focused on the sensing and optoelectronic devices.
Yanjie Wu received her M.S. degree from Jilin Normal University in 2018. She obtained her Ph.D. degree in physics electronics from Jilin University in 2021. Her current research focus on the design of perovskite and Cu2ZnSn(S,Se)4 solar cells.
Qingqing Zhou is currently pursuing her Ph.D. under the supervision of Prof. Lin Xu at College of Electronic Science and Engineering, Jilin University. Her current research focus on the design of chemiresistor with high performance.
Zhichong Shi received his M.S. degree from Jilin University in 2019. Currently he is pursuing her Ph.D. under the supervision of Prof. Hongwei Song at College of Electronic Science and Engineering, Jilin University. His current research interests focus on adjusting the light response, efficient perovskite solar cells.
Xinmeng Zhuang received her B.S. degree from Heilongjiang University in 2018. Currently she is pursuing her Ph.D. under the supervision of Prof. Hongwei Song at College of Electronic Science and Engineering, Jilin University. Her current research interests mainly focus on nanomaterial, energy materials, and perovskite solar cells.
Bin Liu received his B.S. degree in science from Jilin University in 2018. In the same year, he studied under Professor Hongwei Song at Jilin University for postgraduate studies. Currently a doctoral student, his main research direction is perovskite solar cells and organic light-emitting diodes.
Biao Dong obtained his Ph.D. degree in 2008, from Chinese Academy of Science. From 2012 to 2014, he worked as a post-doctor in Laboratoire Catalyse et Spectrochimie (LCS) de l′Université de Caen (France). Currently, he serves as a professor in Jilin University, and has published more than 100 SCI-index papers. His research fields focus on optical properties of rare earth doped nanomaterials and the bioapplications.
Xue Bai obtained her Ph.D. degree in 2008, from Chinese Academy of Science. From 2011 to 2014, she worked as a post-doctor in the department of chemistry in CICECO, University of Aveiro (Portugal). Currently, she serves as a professor in Jilin University, and has published more than 100 SCI-index papers. Her research interests focus on spectral physics of rare earth ions and semiconductor nanomaterials, optoelectronics and its application.
Wen Xu earned his B.S. degree in 2009 and received his Ph.D. in 2014 from Jilin University. From 2015 to 2018, he worked as research fellow in Nanyang Technological University, and JSPS research fellow in Tokyo Institute of Technology, respectively. His research interests focus on luminescent materials, plasmonics and photo-electric devices.
Donglei Zhou received his Ph.D. degree from Jilin University in 2018. Currently, he works as a postdoctoral researcher in Nanyang Technological University, Singapore. Currently, he serves as a professor in Jilin University. His research interests focus on spectral physics of rare earth ions and perovskite solar cells.
Hongwei Song received his Ph.D. degree in Condensed Material Physics from Changchun Institute of Physics, Chinese Academy of Science (CAS) in 1996. From 1996 to 2000, he worked as a postdoctoral researcher in Institute of Physics, CAS, Nagoya Institute of Technology, and University of California at Berkeley in turn. From 2007 he works in Jilin University as a full professor. He is currently the editorial advisory board member of Scientific Reports. He has published over 300 scientific papers and two book chapters. His research interests have been focused on spectral physics of rare earth ions, optoelectronics and its application.