Hydrogen peroxide-modified SnO2 as electron transport layer for perovskite solar cells with efficiency exceeding 22%

Tin oxide (SnO2) as an electron transport layer (ETL) has made impressive achievements in planar-structure heterojunction perovskite solar cells (PSCs). However, the improvement of the SnO2 quality, connected with its trap density, electrical conductivity and band energy alignment, is still worth concerning. The quality of the SnO2 film especially from wet coating techniques is quite sensitive to the environment conditions in the preparation process thus leading to poor repeatability. High repeatability of every functional layer fabrications is one of the basic requirements toward commercialization for PSCs. Herein, we add hydrogen peroxide (H2O2) into the SnO2 precursor solution (denoted as H2O2–SnO2) to enable the quality improvement of ETL. The resultant H2O2–SnO2 film exhibits less trap density, improved electrical conductivity, outstanding film fabrication repeatability and better energy level alignment, leading to significantly higher charge carrier extraction and reduced device hysteresis effect. By employing H2O2–SnO2 ETL, PSCs with excellent repeatability and performance uniformity deliver a champion power conversion efficiency (PCE) of 22.15% with negligible hysteresis, and show impressive long-term stability. This research paves a new way for the further performance enhancement of planar PSCs and the higher quality modified SnO2 may find applications in other opto-electronic devices.