Interface and Depth-dependent Study of Halide Perovskite Semiconductors for Improved Optoelectronics

Abstract

Lead halide perovskites are one of the most promising candidates for solar cells with high absorption coefficients, tunable bandgaps, and excellent charge transport properties. However, these materials still suffer from issues such as phase segregation and interfacial defects, leading to reduced solar cell’s stability. Here we develop a variety of instrument-based techniques to study perovskite phase segregation and the interface chemistry of perovskite. We observed both vertical and lateral cation segregation on mixed-cation perovskite, with non-emissive δ-CsPb(IxBrx)3 cluster on the surface, and FA-rich perovskite underneath, leading to accelerated light-induced degradation on those heterogeneities. Then we found perovskite surface passivation with AEAPTMS vacuum treatment greatly enhances perovskite device’s performance, due to the AEAPTMS-FA+ reaction on the perovskite surface. Finally, we developed a fast, in-situ and nondestructive method toprobe the degradation behavior on the buried interface with UV treatment. With multiwavelength excitation, we can study the depth-dependent information on perovskite and the HTL site is most affected by UV exposure.