Octylammonium Octyldithiocarbamate Assisted Modulation of Crystallization and Doping of In Situ‐Generated Lead Sulfide for Efficient and Highly Stable Carbon‐Based CsPbIBr2 Solar Cells

Abstract Perovskite silicon tandem solar cells are one of the effective ways to further improve the photoelectric conversion efficiency (PCE) in the research and development of solar cells in the future. CsPbIBr2 can be used as the top cell material in tandem solar cells due to its wider bandgap and better long‐term stability. However, the serious defect density and carrier recombination limit its further improvement. In this work, Octylammonium Octyldithiocarbamate (ODTC) is added to the CsPbIBr2 precursor. Through its strong metal ion complexing ability, it combines with the uncoordinated Pb2+ in the CsPbIBr2, and then thermally decomposes to produce PbS during the annealing process. As an additive, ODTC modulates the crystallization of CsPbIBr2, increases the crystal size, reduces defect density, extends carrier lifetime, and improves charge transfer. Moreover, in situ‐generated PbS can also optimize photovoltaic performance of CsPbIBr2 perovskite solar cell (PSC). Consequently, the champion PCE of the devices can attain to 10.15% and still maintain an initial efficiency of 90% after 45 days. Therefore, the strategy is an effective way to prepare efficient and stable CsPbIBr2 PSCs.