Photophysics of Perovskite Solar Cells based on Sn-TiO2 Electron Extraction Layer Revealed by Time-Resolved Photoluminescence Spectroscopy

摘要

In recent years, perovskite solar cells (PSCs) have attracted increasing attention owing to its easy fabricated and high solar energy harvesting efficiency. According to the report of national renewable energy laboratory (NREL), the power conversion efficiency (PCE) of PSCs has rapidly improved from 3.8% to 24.2% in a few years. Many research groups dedicated to optimizing the device by facilitating carrier transport between each layer. By doping metal ion into TiO2 electron extraction layer, the interface defects between electron extraction and halide perovskite film could be decreased. Though the PSCs performance has been successfully enhanced, there is a lack of the fundamental understanding of the photophysics in perovskite. In this work, we used tin (Sn) ions doped TiO2 as electron extraction layer for PSCs. We study the electron excitation behavior of PSCs based on Sn-TiO2 electron extraction layer through time-resolved photoluminescence spectroscopy (TRPL), and we can estimate a photo-induced carrier injection from the halide perovskite film to the Sn-TiO2 electron extraction layer. By PL and TRPL measurements, we can obtain fast decay time, slow decay time, and PL average lifetime. Hence, we can demonstrate the charge separation behavior and reduced radiative electron-hole recombination behavior. The results show the superior electron excitation characteristic for Sn-TiO2 that is promising for raising the photovoltaic performance of PSCs.