Low-temperature processing of polyvinylpyrrolidone modified CsPbI2Br perovskite films for high-performance solar cells

Owing to the inevitability of moisture/thermal instability in organic-inorganic hybrid perovskites, pure inorganic perovskites such as CsPbI 2 Br perovskite have surfaced as promising options for commercial perovskite solar cells (PSCs) due to their high photovoltaic performance and excellent inherent stability. However, designing additive engineering approaches to mitigate defect-induced crystalline phase transitions from a photosensitive perovskite phase to a non-perovskite phase has been a difficult task for researchers. In this work, using a one-step spin coating approach, we have prepared a polyvinylpyrrolidone (PVP) polymer-incorporated stable phase of CsPbI 2 Br at a low temperature (120 ​°C). Examinations using structural, morphological, and photo-physical measurements revealed that the optimum amount of PVP can greatly improve the optoelectronic properties of the film, which facilitates in reducing the trap states and defect in perovskite film, thus enabling charge carrier separation and suppressing charge recombination. As a result, the device based on 5 ​mg-PVP achieves a champion power conversion efficiency (PCE) of 10.47%, with a fill factor (FF) of 56.35%, a short-circuit current (J SC ) of 18.47 ​mA ​cm 2 , and an open-circuit voltage (V OC ) of 1.01 ​V, which is significantly higher than the device without PVP (6.36%). These findings suggest that PVP-CsPbI 2 Br has tremendous promise for future research and application in photovoltaic devices. • Low-temperature processing of CsPbI 2 Br perovskite films using PVP additive. • Formation of compact, dense, and defect-free perovskite film. • Optimum amount of PVP is crucial for facilitating precursor diffusion to generate the required phase at low temperature. • The champion device yielded a PCE of 10.47%, with a J SC of 18.47 ​mA ​cm 2 .