CH3NH3+ and Pb immobilization through PbI2 binding by organic molecule doping for homogeneous organometal halide perovskite films

Abstract

Organic molecule doping is one of the main strategies to enhance the performance and sustainability of organometal halide perovskite polycrystalline films. However, the mechanisms for interpreting organic molecule doping are poorly understood, limiting the development of perovskite solar cells (PSCs). Herein, we revisit regular perovskite films and study the doping effects of two typical organic molecules. With PCBM and PMMA doping, the CH₃NH₃PbI₃ films showed higher homogeneity in their crystalline structure, chemical composition, surface topography and potential. The binding of organic molecules to PbI₂ inhibited the migration of Pb and the aggregation of CH₃NH₃⁺ vacancies. PMMA induced the formation of CH₃NH₃PbI₃ nanofibers, which bridged the grains and increased the intergrain connectivity. The CH₃NH₃PbI₃ films doped with organic molecules showed a five-fold increase in photoexcited carrier lifetime (>1 μs) with an enhanced photoelectric conversion efficiency and stability. Our work offers insight into the doping of organic molecules in perovskite films and paves the way for the further optimization of PSCs.