Black Phosphorus Quantum Dots Induced High‐Quality Perovskite Film for Efficient and Thermally Stable Planar Perovskite Solar Cells

Crystallinity and trap‐state density of a perovskite film play a critical role in the performance of corresponding perovskite solar cells (PVSCs). Herein, liquid‐phase‐exfoliated black phosphorus quantum dots (BPQDs) are incorporated into the perovskite precursor solution as additives to direct the formation of the perovskite film, i.e., methylammonium lead iodide (MAPbI 3 ). It is found that the perovskite films made with BPQDs have higher crystallinity and less nonradiative detects compared with the pristine ones, leading to longer carrier lifetime and higher carrier collection efficiency. Time‐of‐flight secondary‐ion mass spectra and surface density calculation of BPQDs reveal that the improvement of the perovskite film quality may be related to the heterogeneous nucleation of the perovskite film at the BPQDs. PVSCs using MAPbI 3 films made with BPQDs achieve a maximum power conversion efficiency of 20.0% and an encouraging thermal stability of T 80 = 100 h at 100 °C. Both values are remarkably higher than the devices with pristine perovskite films. Therefore, this work demonstrates the potential of the 2D materials quantum dots‐assisted growth method for high‐performance PVSCs.