All‐Inorganic CsPbI₂Br Perovskite Solar Cells: Recent Developments and Challenges

Abstract

In the past decade, organic–inorganic halide perovskites (OIHPs) perovskite solar cells (PSCs) have received gigantic research attention owing to their prompt development in power conversion efficiency (PCE) from the initial 3.8% for the first prototype in 2009 to the present state‐of‐the‐art value of 25.5%. However, due to the weak‐bonded organic components in the hybrid crystal structure, the intrinsic chemical instability of OIHPs persuaded by humidity, ultraviolet light, and heat remain a challenging issue for them to meet industrialization‐specific requirements. Parallel to the flourishing of OIHPs, the progress of inorganic cesium‐based metal halide PSCs (CsPbX3, X = I, Br, and mixed) is hastening with PCEs over 20%. Due to its excellent stability under thermal and high humidity conditions, CsPbI2Br is one of the most fascinating inorganic perovskites and a notable research hotspot in the field of perovskite photovoltaics (PV). Herein, recent developments of CsPbI2Br‐based PSCs including the optoelectronic properties, processing methods for preparing CsPbI2Br films, stability of devices, and efficiency improvements are reviewed and deliberated. Finally, cutting‐edge engineering approaches for optimizing the PV performance are discussed and new challenges and perspectives for future research in this field are recognized.

Efficiency Potential and Voltage Loss of Inorganic CsPbI2Br Perovskite Solar Cells

“…Almost all published p–i–n CsPbI 2 Br solar cells use NiO x as HTL with some exceptions using P3HT and P3CT. [ 21 ] For the first time, we produced CsPbI 2 Br solar cells using MeO–2PACz as HTL, see Figure a. Figure 4b shows an SEM image of a perovskite film on MeO–2PACz, revealing a dense and pinhole‐free film.…”

“…The majority of published reports on CsPbI 2 Br perovskite compositions have used n–i–p device architectures with TiO 2 , SnO 2 , or ZnO as ETL and spiro‐OMeTAD, PTAA, or P3HT as HTL. [ 21 ] The metal oxide ETLs typically need annealing temperatures above 200 °C. In the long run, inorganic perovskites might be integrated as top cells into tandem solar cell devices with temperature‐sensitive bottom cells.…”

Designing Multifunctional Donor–Acceptor-Type Molecules to Passivate Surface Defects Efficiently and Enhance Charge Transfer of CsPbI2Br Perovskite for High Power Conversion Efficiency

“…All-inorganic mixed-halide perovskite CsPbI 2 Br with excellent thermally stability and a suitable band gap (1.82∼1.92 eV) − is one of the most promising optoelectronic materials for application of light-emitting diodes , and perovskite solar cells (PSCs). , It was reported that the power conversion efficiency (PCE) of PSCs based on CsPbI 2 Br has reached 18.06%, which was comparable with that of other high-performance all-inorganic PSCs. However, the energy loss ( E loss ) of CsPbI 2 Br (>0.52 eV) was still much higher than that of organic–inorganic hybrid perovskites (≈0.39 eV), which limits its improvement of PCE.…”

Restructuring and Reshaping of CsPbX3 Perovskites by Lithium Salts

“…The d-spacing of 2.1 Å for triangles fits the deltaphase structure whereas the d-spacing of 3.2 Å measured of the rods indicates the emergence of an orthorhombic perovskite CsPbI 2 Br. [23,24] The directional growth would be explained by the anisotropic structure of the CsPbI 2 Br, with iodine centered on four faces of the crystal lattice and cesium centered on the other two. This is similar to the self-assembly of orthorhombic CsPbI 3 nanowires that has been previously observed with the use of polar solvents for perovskite nanocubes.…”