Enhanced Electronic Properties of SnO₂ <i>via</i> 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

CH₃NH₃PbBr₃ Quantum Dot-Induced Nucleation for High Performance Perovskite Light-Emitting Solar Cells

Solution-processed organometallic halide perovskites have obtained rapid development for light-emitting diodes (LEDs) and solar cells (SCs). These devices are fabricated with similar materials and architectures, leading to the emergence of perovskite-based light-emitting solar cells (LESCs). The high quality perovskite layer with reduced nonradiative recombination is crucial for achieving a high performance device, even though the carrier behaviors are fundamentally different in both functions. Here CH₃NH₃PbBr₃ quantum dots (QDs) are first introduced into the antisolvent in solution phase, serving as nucleation centers and inducing the growth of CH₃NH₃PbI₃ films. The heterogeneous nucleation based on high lattice matching and a low free-energy barrier significantly improves the crystallinity of CH₃NH₃PbI₃ films with decreased grain sizes, resulting in longer carrier lifetime and lower trap-state density in the films. Therefore, the LESCs based on the CH₃NH₃PbI₃ films with reduced recombination exhibit improved electroluminescence and external quantum efficiency. The current efficiency is enhanced by 1 order of magnitude as LEDs, and meanwhile the power conversion efficiency increases from 14.49% to 17.10% as SCs, compared to the reference device without QDs. Our study provides a feasible method to grow high quality perovskite films for high performance optoelectronic devices