Synergistic Surface Defect Passivation of Ionic Liquids for Efficient and Stable MAPbI₃-Based Inverted Perovskite Solar Cells

Abstract

Organic−inorganic hybrid perovskite solar cells are fabricated using polycrystalline perovskite thin films, which possess high densities of point and surface defects. The surface defects of perovskite thin films are the key factors that affect the device performance. Therefore, the reduction of harmful defects is the primary task for improving device performance. Therefore, in this study, high-quality perovskite thin films are prepared using an ionic liquid, dithiocarbamate diethylamine (DADA), to passivate the interface. The electron-rich sulfur atom in the DADA molecule chelates with the uncoordinated lead ion in the perovskite films, and the diethylammonium cation forms a hydrogen bond with the free iodine ion, which further improves the passivation. The synergistic passivation and improved morphology of the perovskite thin films substantially reduce the number of charged defects on the film surface and prolong the carrier lifetime. In addition, the DADA surface treatment increases the work function of the perovskite film, which is beneficial for carrier transport. Under standard solar-lighting conditions, the power conversion efficiency (PCE) of the device increases from 19.13 to 21.36%, and the fill factor is as high as 83.17%. Owing to both the hydrophobicity of DADA molecules and the passivation of ion defects, the PCE of the device remains above 80%, even for the device stored for 500 h in air at a relative humidity of 65%, and the device stability is substantially improved.

Synergistic Enhancement of Stability and Performance for Perovskite Solar Cells Using Fluorinated Benzoic Acids as Additives

“…Among the single‐junction PSCs, the PCE of most MAPbI 3 ‐based PSCs ranges from 13.7% to 22.1%. [ 15–23 ] However, the long‐term stability of PSCs still cannot meet the stringent commercialization requirements because perovskites often experience substantial efficiency losses when exposed to environmental factors such as oxygen, heat, light illumination, and humidity. [ 24–26 ] Specifically, due to high volatility of methyl ammonium (MA) ions in high temperature and humid environments, structural degradation of the active layer may result in perovskite crystal decompositions into PbI 2 and undercoordinated ions, leading to a reduced conductivity or, in the worst case, complete loss of efficiency.…”