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.