Low Temperature Processed SnO₂ Electron Transporting Layer from Tin Oxalate for Perovskite Solar Cells

SnO2 has been widely recognized as an indispensable electron transporting layer for perovskite solar cells. Therefore, a lot of research interest has been paid to fabricate low temperature flexible perovskite solar cells using SnO2 electron transporting layers. Previous solution processed low temperature SnO2 electron transporting layers usually rely on presynthesized SnO2 nanocrystals or complicated post-treatments, which are quite expensive. Herein, we have demonstrated a facile solution processed method for depositing SnO2 electron transporting layers at a low temperature of 100 °C using tin oxalate and hydrogen peroxide. We find that a low volume of hydrogen peroxide is critical for depositing SnO2 electron transporting layers with superior film quality. After optimizing the hydrogen peroxide volume, perovskite solar cells using our SnO2 electron transporting layer can demonstrate a champion performance of 21.32%; at the same time, the perovskite solar cell can maintain 99.0% of its initial power conversion efficiency after storage for 60 days. Therefore, our method has great potential to be applied in flexible PSCs in the future.