Imidazole as an Amphoteric Lewis Acid-Base Additive for Efficient CsPbI3 Inorganic Perovskite Solar Cells

Inorganic perovskite CsPbI3 is regarded as a promising substitution of organic-inorganic hybrid perovskite because of its high thermal stability. To achieve high-performance and stable perovskite solar cells (PSCs), CsPbI3 films with large grains and low trap densities are required. In this paper, amphoteric imidazole with synergistic properties of Lewis acid and base is introduced to improve the quality of low-temperature processed CsPbI3 films. Imidazole is prone to form strong coordination with Pb2+ and I- in perovskites through a Lewis acid-base interaction, delaying the crystallization rate of CsPbI3 films. This results in enlarged grains, improved crystallinity, and suppressed formation of defects at grain boundaries. The power conversion efficiency of PSCs increases from 13.12% (control group) to 14.88% (imidazole-containing group) with improved stability. This work provides a facile strategy to improve the performance of low-temperature processed CsPbI3 PSCs.