Surface modification of CsPbI2Br for improved performance of inorganic perovskite solar cells

Degradation of halide perovskite materials upon ambient exposure is one of the major challenge for their applications. Inorganic perovskite materials (such as CsPbI2Br) have emerged as potential candidate for stable perovskite optoelectronic applications in recent years owing to their appropriate bandgap and high thermal stability. However, the fabrication of high quality CsPbI2Br absorber layer is the main challenge to achieve highly efficient perovskite solar cells (PSCs). Herein, we report a strategy for the surface modification of CsPbI2Br layer via the treatment with isopropanol. The modified CsPbI2Br absorber layer has energetically more favorable band alignment with the C60 which facilitates the efficient charge transfer and mitigate the energy loss at CsPbI2Br/C60 interfaces. The inorganic PSCs with the architecture of ITO/NiOx/CsPbI2Br/C60/Cu showed open-circuit voltage (VOC) of 1.13 V and 30% improvement in the power conversion efficiency (PCE). Moreover, the devices exhibit less hysteresis index and excellent stability with no sign of degradation for 160 h.