Interfacial stability of perovskite solar cell layers

Abstract

Organometal halide (OMH) perovskites are chemically unstable when exposed to oxygen, heat, and moisture. The long term stability of organometal halide perovskite solar cells (PSCs) may be enhanced by understanding two interactions. The first is between the perovskite and the electron transport layer (ETL). The second is between the perovskite and the hole transport layer (HTL). It has been reported that the ionic defects in the perovskite layer (for example, iodine ions) may drift to and accumulate at the interfacial areas of the ETL and the HTL over time, leading to extensive chemical degradation of PSCs. In this project, we adopt ultraviolet-visible (UV-Vis) absorption and steady-state photoluminescence (PL) emission spectra to investigate the degradation processes of two OMH perovskites, methylammonium lead iodide (MAPbI3), and methylammonium lead bromide (MAPbBr3) with the aim to understand the exact effects of ion migration and accumulation at ETL and HTL on long term stability of perovskites. Our research reveals that the interaction of the migrated ions with TiO2 ETL significantly accelerates the degradation of both OMH perovskites, while the interfacial interactions at spiro-OMeTAD (2,2',7,7'-Tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'spirobifluorene) HTL yield lesser effect on the stability of perovskites. The results also suggest ion accumulation at the ETL/HTL affects the interfacial charge transfer processes.