Trimethyl Ammonium-Assisted Interfacial Modification for Efficient and Stable Wide-Bandgap Perovskite Solar Cells

Wide-bandgap (WBG) perovskite solar cells (PSCs) are acknowledged as promising candidates for tandem solar cells and building photovoltaics. It is well known that cesium-based all-inorganic halide WBG perovskites possess the comparable optoelectronic properties as the organic–inorganic counterparts, but exhibit superior thermal stability. Among them, CsPbIBr 2 is considered a feasible material for tandem solar cells after balancing the bandgap and stability of the inorganic perovskite. However, CsPbIBr 2 PSCs are often subjected to drastic interfacial charge recombination especially in carbon-based device structure derived from the chemical bonding defects (i.e., uncoordinated Pb 2+ ) naked on CsPbIBr 2 soft lattice, which dramatically limits overall efficiency of CsPbIBr 2 WBG PSCs. Herein, a trimethyl ammonium salt hexyltrimethylammonium bromide is presented for CsPbIBr 2 /carbon interfacial modification. Benefiting from the −N + (CH 3 ) 3 passivation effect and −C 6 H 13 hydrophobic alkyl chain, the optimal device with highly smooth morphology and sufficient charge extraction exhibits a champion power conversion efficiency of 11.24% and improved long-term stability with 99.7% and 79.7% efficiency retention under dry air atmosphere and continuous 85 °C thermal stress, indicating the valuable potential application of the lattice solidified CsPbIBr 2 WBG PSCs.