SnO 2 –Carbon Nanotubes Hybrid Electron Transport Layer for Efficient and Hysteresis‐Free Planar Perovskite Solar Cells

Tin oxide (SnO 2 ) has recently received increasing attention as an electron transport layer (ETL) in planar perovskite solar cells (PSCs) and is considered a possible alternative to titanium oxide (TiO 2 ). However, planar devices based on pure solution‐processed SnO 2 ETL still have hysteresis, which greatly limits the application of SnO 2 in high‐efficiency solar cells. Herein, to address this issue, a hybrid ETL of SnO 2 and carbon nanotubes (CNTs) is fabricated by a simple thermal decomposing of a mixed solution of SnCl 4 ·5H 2 O and pretreated CNTs (termed SnO 2 –CNT). The addition of CNTs can significantly improve the conductivity of SnO 2 films and reduce the trap‐state density of SnO 2 films, which benefit carrier transfer from the perovskite layer to the cathode. As a result, a high efficiency of 20.33% is achieved in the hysteresis‐free PSCs based on SnO 2 –CNT ETL, which shows 13.58% enhancement compared with the conventional device (power conversion efficiency = 17.90%).