Optimization of Bulk Defects in Sn/Pb Mixed Perovskite Solar Cells Through Synergistic Effect of Potassium Thiocyanate

The organic-inorganic Sn-Pb mixed perovskite has achieved great progress during the last 10 years and is considered as one of the most promising low-bandgap photovoltaic materials. It has lower toxicity, outstanding optoelectrical properties, and achieved remarkable performance. However, there are still plenty of challenges in controlling the morphology, crystallinity, and defects of the Sn-Pb mixed perovskite film because of the inferior chemical stability of Sn compared with Pb. Herein, it is found that the synergistic effect of potassium thiocyanate (KSCN) in the Sn-Pb mixed perovskites can enlarge the grain size, enhance the crystallization, improve the film morphology, and obtain high-quality perovskite films which effectively eliminate the bulk defects and smooth carrier transportation of Sn-Pb mixed perovskite solar cells. Through optimizing the concentration of KSCN, a high-performance MA(0.5)FA(0.5)Pb(0.5)Sn(0.5)I(3) solar cell with an efficiency of 15.14% and improved stability is obtained. This work lays a key foundation for the fabrication of efficient and stable Sn-based or Sn-Pb mixed perovskite solar devices.