Enhanced Electronic Properties of SnO₂ via Electron Transfer from Graphene Quantum Dots for Efficient Perovskite Solar Cells

Tin dioxide (SnO₂) has been demonstrated as an effective electron-transporting layer (ETL) for attaining high-performance perovskite solar cells (PSCs). However, the numerous trap states in low-temperature solution processed SnO₂ will reduce the PSCs performance and result in serious hysteresis. Here, we report a strategy to improve the electronic properties in SnO₂ through a facile treatment of the films with adding a small amount of graphene quantum dots (GQDs). We demonstrate that the photogenerated electrons in GQDs can transfer to the conduction band of SnO₂. The transferred electrons from the GQDs will effectively fill the electron traps as well as improve the conductivity of SnO₂, which is beneficial for improving the electron extraction efficiency and reducing the recombination at the ETLs/perovskite interface. The device fabricated with SnO₂:GQDs could reach an average power conversion efficiency (PCE) of 19.2 ± 1.0% and a highest steady-state PCE of 20.23% with very little hysteresis. Our study provides an effective way to enhance the performance of perovskite solar cells through improving the electronic properties of SnO₂.