Mechanism and effect of γ-butyrolactone solvent vapor post-annealing on the performance of a mesoporous perovskite solar cell

Abstract

In this paper, γ-butyrolactone (GBL) solvent vapor post-annealing (SVPA) on CH₃NH₃PbI₃ thin films is reported, aiming to improve the complete transformation of PbI₂ and increase the grain size of the CH₃NH₃PbI₃ crystal, thus boosting the performance of mesoporous CH₃NH₃PbI₃ perovskite solar cells (PSCs). The influence of GBL SVPA on the microstructure of perovskite layers and performance of PSCs was studied. The short circuit current density (J_sc) of the devices significantly increased, yielding a high efficiency of 16.58%, which was 27.05% higher than that of thermally annealed films. A model was derived to explain the effect of GBL SVPA on PSCs. The perovskite films prepared by this method present several advantages such as complete transformation of PbI₂ to CH₃NH₃PbI₃, high crystallinity, large grain size, and fewer grain boundaries than those prepared without GBL SVPA. This improvement is beneficial for charge dissociation and transport in hybrid photovoltaic devices.