Inorganic Halide Perovskite Solar Cells: Progress and Challenges

Multi-junction (tandem) solar cells (TSCs) consisting of multiple light absorbers with considerably different band gaps show great potential in breaking the Shockley–Queisser (S–Q) efficiency limit of a single junction solar cell by absorbing light in a broader range of wavelengths. Perovskite solar cells (PSCs) are ideal candidates for TSCs due to their tunable band gaps, high PCE up to 25.2%, and easy fabrication. PSCs with high PCEs are typically fabricated via a low temperature solution method, which are easy to combine with many other types of solar cells like silicon (Si), copper indium gallium selenide (CIGS), narrow band gap PSCs, dye-sensitized, organic, and quantum dot solar cells. As a matter of fact, perovskite TSCs have stimulated enormous scientific and industrial interest since their first development in 2014. Significant progress has been made on the development of perovskite TSCs both in the research laboratories and industrial companies. This review will rationalize the recent exciting advancement in perovskite TSCs. We begin with the introduction of the historical development of TSCs in a broader context, followed by the summary of the state-of-the-art development of perovskite TSCs with various types of device architectures. We then discuss the strategies for improving the PCEs of perovskite TSCs, including but not limited to the design considerations on the transparency of perovskite absorbers and metal electrodes, protective layers, and recombination layers (RLs)/tunnel junctions (TJs), with a particular focus on the band gap tuning and thickness adjustment of active layers. We subsequently introduce a range of measurement techniques for the characterization of perovskite TSCs. We also cover other core issues related to the large-scale applications and commercialization. Finally, we offer our perspectives on the future development of emerging photovoltaic technologies as the device performance enhancement and cost reduction are central to almost any type of solar cell applied in the perovskite TSCs.

Perovskite Tandem Solar Cells: From Fundamentals to Commercial Deployment

Recent research shows that the interface state in perovskite solar cells is the main factor which affects the stability and performance of the device, and interface engineering including strain engineering is an effective method to solve this issue. In this work, a CsBr buffer layer is inserted between NiO x hole transport layer and perovskite layer to relieve the lattice mismatch induced interface stress and induce more ordered crystal growth. The experimental and theoretical results show that the addition of the CsBr buffer layer optimizes the interface between the perovskite absorber layer and the NiO x hole transport layer, reduces interface defects and traps, and enhances the hole extraction/transfer. The experimental results show that the power conversion efficiency of optimal device reaches up to 19.7% which is significantly higher than the efficiency of the device without the CsBr buffer layer. Meanwhile, the device stability is also improved. This work provides a deep understanding of the NiO x /perovskite interface and provides a new strategy for interface optimization.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/advs.201903044

NiO/Perovskite Heterojunction Contact Engineering for Highly Efficient and Stable Perovskite Solar Cells

Perovskite solar cells (PSCs) have become a promising photovoltaic (PV) technology, where the evolution of the electron-selective layers (ESLs), an integral part of any PV device, has played a distinctive role to their progress. To date, the mesoporous titanium dioxide (TiO2 )/compact TiO2 stack has been among the most used ESLs in state-of-the-art PSCs. However, this material requires high-temperature sintering and may induce hysteresis under operational conditions, raising concerns about its use toward commercialization. Recently, tin oxide (SnO2 ) has emerged as an attractive alternative ESL, thanks to its wide bandgap, high optical transmission, high carrier mobility, suitable band alignment with perovskites, and decent chemical stability. Additionally, its low-temperature processability enables compatibility with temperature-sensitive substrates, and thus flexible devices and tandem solar cells. Here, the notable developments of SnO2 as a perovskite-relevant ESL are reviewed with emphasis placed on the various fabrication methods and interfacial passivation routes toward champion solar cells with high stability. Further, a techno-economic analysis of SnO2 materials for large-scale deployment, together with a processing-toxicology assessment, is presented. Finally, a perspective on how SnO2 materials can be instrumental in successful large-scale module and perovskite-based tandem solar cell manufacturing is provided.

Tin Oxide Electron‐Selective Layers for Efficient, Stable, and Scalable Perovskite Solar Cells

Toward development of high-performance perovskite solar cells based on CH3NH3GeI3 using computational approach

Device simulation of inverted CH3NH3PbI3−xClx perovskite solar cells based on PCBM electron transport layer and NiO hole transport layer

The perovskite solar cells attracted great attention owing to their low cost and high performance. SnO2 as electron transport layer has been mostly used in the perovskite solar cells due to its exc...

NumericalSimulation of Planar Heterojunction PerovskiteSolar Cells Based on SnO 2 Electron Transport Layer

Interface engineering has been regarded as an effective and noninvasive means to optimize the performance of perovskite solar cells (PSCs). Here, doping engineering of a ZnO electron transport layer (ETL) and CsPbI3/ZnO interface engineering via introduction of an interfacial layer are employed to improve the performances of CsPbI3-based PSCs. The results show that when introducing a TiO2 buffer layer while increasing the ZnO layer doping concentration, the open-circuit voltage, power conversion efficiency, and fill factor of the CsPbI3-based PSCs can be improved to 1.31 V, 21.06%, and 74.07%, respectively, which are superior to those of PSCs only modified by the TiO2 buffer layer or high-concentration doping of ZnO layer. On the one hand, the buffer layer relieves the band bending and structural disorder of CsPbI3. On the other hand, the increased doping concentration of the ZnO layer improves the conductivity of the TiO2/ZnO bilayer ETL because of the strong interaction between the TiO2 and ZnO layers. However, such phenomena are not observed for those of a PCBM/ZnO bilayer ETL because of the weak interlayer interaction of the PCBM/ZnO interface. These results provide a comprehensive understanding of the CsPbI3/ZnO interface and suggest a guideline to design high-performance PSCs.

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Peng Zhao

Papers

Device simulation of inverted CH3NH3PbI3−xClx perovskite solar cells based on PCBM electron transport layer and NiO hole transport layer

NumericalSimulation of Planar Heterojunction PerovskiteSolar Cells Based on SnO 2 Electron Transport Layer

Optimizing the Performance of CsPbI3-Based Perovskite Solar Cells via Doping a ZnO Electron Transport Layer Coupled with Interface Engineering

Theoretical Analysis of Two‐Terminal and Four‐Terminal Perovskite/Copper Indium Gallium Selenide Tandem Solar Cells

The crystal anisotropy effect of MAPbI3 perovskite on optoelectronic devices