Modifying perovskite solar cells with l(+)-cysteine at the interface between mesoporous TiO₂ and perovskite

Perovskite solar cells (PSCs) have attracted extensive attention and their which power conversion efficiency (PCE) has rapidly increased from 3.8% to 25.2% in recent years. Interfacial modification is regarded as a highly effective strategy to address the humidity instability and improve the performance of PSCs. In this regard, L(+)-cysteine (L-cy), a typical trifunctional amino acid, is employed to modify the interface between mesoporous TiO2 (mp-TiO2) and perovskite. The incorporation of L-cy increases the PCE from 11.5% to 14.4%. Fluorescence measurements show that the electron injection from perovskite to mp-TiO2 is enhanced due to the interactions between the functional groups (–COOH, –NH2 and –SH) of L-cy and Ti4+ ions in mp-TiO2 and unsaturated Pb2+ and I− ions in the perovskite film. This work demonstrates a facile and effective method to achieve high-performance PSCs.