Self-Induced A-B-A Structure Enables Efficient Wide-Bandgap Perovskite Solar Cells and Tandems

Wide-bandgap (WBG) perovskite solar cells (PSCs), due to their tunable bandgap, can be integrated into tandem cell configurations with narrow-bandgap solar cells to overcome the shockley-queisser (SQ) limitation. However, the main obstacles limiting their performance are poor crystallinity and light-induced halide segregation. To achieve high performance in WBG PSCs, this study reports a dual-molecule cooperative strategy involving the introduction of 1-benzyl-3-methylimidazolium bromide (BzMIM Br) as an additive and the introduction of 6-fluoropyrimidine-2,4- diamine (DMFP) as a passivation layer. DMFP self-induced penetration to the bottom of the perovskite, forming an A-B-A structure with BzMIM Br, through utilizing multisite integration with uncoordinated Pb²⁺, constructing internal molecular bridges. Research findings indicate that the A-B-A structure with uniform potential distribution can interact with the perovskite in a step-like manner, suppressing halide segregation, and replenishing the vacancy defects. Results demonstrate power conversion efficiencies (PCEs) of 22.77% and 18.54% for inverted PSCs with effective areas of 0.043 and 1.0 cm², respectively. Unencapsulated devices retain 95% of initial efficiency after 1500 h of continuous illumination under one-sun equivalent conditions in a nitrogen atmosphere. Additionally, the PCE of the prepared semi-transparent WBG devices reached 19.60%, while the PCE of the 4-terminal all-perovskite tandem device reached 26.18%.