Composite SnO2-K2S ETL for Energy Level Regulation and Electron Mobility Enhancement in Perovskite Solar Cells

Abstract

Perovskite solar cells with high performance are generally based on SnO2 as electron transport layer. SnO2 layer is crucial for the crystallization and defects regulation of perovskite, and has a significant impact on device performance. Energy level mismatch and oxygen vacancies are significant challenges for SnO2. Moreover, defects at buried interface (SnO2/perovskite) hinder the device photovoltaic performance. To optimize SnO2 layer, we found the incorporation of K2S into the SnO2 layer effectively regulated the energy levels and occupied oxygen vacancies. Moreover, electron mobility of SnO2-K2S composite electron transport layer was enhanced, and the interface quality was also improved, promoting efficient electron extraction and transport. Additionally, the crystallization rate of perovskite was reduced to obtain large grain size. The defects at buried interface and within perovskite layer were passivated, that the trap state density was decreased, which suppressing carrier recombination. Consequently, the device based on SnO2-K2S electron transport layer showed an enhanced photovoltaic performance with power conversion efficiency of to 23.28%.