Enhancing efficiency of planar structure perovskite solar cells using Sn-doped TiO2 as electron transport layer at low temperature

Abstract

Sn-doped TiO2 films were successfully deposited by low-temperature solution method as electron transport layer (ETL), whose influence on the performance of perovskite solar cell (PSC) was investigated. In this work, X-ray photoelectron spectroscopy and X-ray diffraction revealed that Sn4+ was successfully incorporated into the TiO2 lattice as an effective metal ion dopant without forming secondary phases. Compared with pristine TiO2, the Sn-doped TiO2 is more efficient for photogenerated electron extraction and transport, showing lower trap-state density and higher conductivity. Higher short-circuit current (Jsc) is obtained due to the enhanced carrier transport velocity and improved charge collection efficiency, leading to a higher fill factor (FF) and better energy transfer efficiency. Our optimized planar solar cell using such a Sn-doped TiO2 ETL has achieved power conversion efficiency (PCE) of 17.2%, which was almost 29.3% higher than that of sample using the undoped TiO2. To the best of our knowledge, this is the lowest processing temperature for Sn-dope TiO2 film at present, which provides an effective route towards flexible high-performance PSCs.