Stable dual cations perovskite nanocrystals as absorbers for perovskite solar cells with efficiencies exceeding 24%

Abstract

Abstract FA 1 − X Cs X PbI 3 (formamidinium [FA]; cesium [Cs]; lead [Pb]; and iodine [I]) perovskites are promising candidates in perovskite solar cells (PSCs) for the superior optoelectronic properties, tunable bandgap, and high thermal stability. It is well known that the preparation of phase‐pure perovskite and hybrid cations and/or halides strategy are effective ways to achieve high efficiency and strengthen the stability of PSCs. In this work, dual cation perovskite precursor Cs 0.05 FA 0.95 PbI 3 was synthesized by a simple and effective one‐step solution process under ambient conditions and successfully used in the PSCs as an active layer. By this strategy, the high‐purity Cs‐FA hybrid cations perovskites not only enhanced power conversion efficiency (PCE) to 22.10% but also achieved long‐term stability. This work explains in detail the effects of Cs + in FAPbI 3 perovskites on precursor chemistry, film nucleation, grain growth, and defect properties. Furthermore, with the incorporation of MACl in the precursor and passivation process, the photovoltaic properties are further enhanced. Encouragingly, the mixed cations PSCs feature the champion PCE of 24.5%, which is one of the highest values reported to date for Cs‐doped PSCs.