SnO2–Carbon Nanotubes Hybrid Electron Transport Layer for Efficient and Hysteresis‐Free Planar Perovskite Solar Cells

Tin oxide (SnO2) 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 (TiO2). However, planar devices based on pure solution‐processed SnO2 ETL still have hysteresis, which greatly limits the application of SnO2 in high‐efficiency solar cells. Herein, to address this issue, a hybrid ETL of SnO2 and carbon nanotubes (CNTs) is fabricated by a simple thermal decomposing of a mixed solution of SnCl4·5H2O and pretreated CNTs (termed SnO2–CNT). The addition of CNTs can significantly improve the conductivity of SnO2 films and reduce the trap‐state density of SnO2 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 SnO2–CNT ETL, which shows 13.58% enhancement compared with the conventional device (power conversion efficiency = 17.90%). A hybrid electron transport layer (ETL) of SnO2 and carbon nanotubes (CNTs) is designed by simple thermal decomposition of a mixed solution of SnCl4·5H2O and pretreated CNTs. Based on the hybrid ETL, a high efficiency of 20.33% is achieved in the hysteresis‐free perovskite solar cell, which shows 13.58% enhancement compared with the conventional device (power conversion efficiency = 17.90%).