The non-radiative recombination loss at the interface is a huge obstacle to improving the photovoltaic performance of perovskite solar cells (PSCs), especially carbon-based PSCs (C-PSCs). Here, we propose a strategy for synergistic regulation of interface defects and carrier transport through functional groups of long-chain ammonium salt molecules to form 2D perovskite passivation layers by surface treatment with 5-aminovalerate hydroiodide (5-AVAI). The results indicate that the carboxyl group (–COOH) in 5-AVAI molecules can form coordination bonds with uncoordinated Pb 2+ ions, thereby anchoring to the surface of the perovskite film. Simultaneously, the electrostatic interaction between the amino group (–NH 3 + ) and I − ions in 5-AVAI inhibits the formation of iodide vacancies, enhances defect passivation, and improves the transport and transfer efficiency of interfacial carriers. The atmospherically generated 5-AVAI-modified C-PSCs exhibited an efficiency of 16.50% and retained 85% of their initial efficiency for 80 days in atmospheric environment.
In the two-step method for perovskite film fabrication, insufficient reaction between organic ammonium salts and PbI 2 affects the active layer quality, resulting in poor power conversion efficiency (PCE). In this work, we introduce pentanamine acetic acid (PenAAc) and 5-aminovaleric acid iodine (5-AVAI) as two efficient additives to modify PbI 2 layer during perovskite films fabrication via the two-step method in an air environment. After additive modifications, the quality of both PbI 2 layers is improved: PenAAc enhances crystallinity and increases PbI 2 grain size, while 5-AVAI induces a uniform and smooth PbI 2 layer. The optimized PbI 2 films facilitate the reaction between PbI 2 and organic salts, yielding a high-quality perovskite layer with enhanced crystallinity and reduced defect density. In contrast, the macromolecule structure of 5-AVAI does not diffuse after annealing, remaining in the PbI 2 layer and exerting minimal influence on the perovskite surface. However, dissociative CH 3 COO − groups in PenAAc molecules diffuse from the PbI 2 layer to the perovskite surface during annealing, forming strong interactions between I - and Pb 2+ with CH 3 COO − groups. This further improves perovskite film quality and accelerates charge carrier extraction/transport in devices. Consequently, additive-modified perovskite solar cells achieve excellent PCEs of 24.50 % (5-AVAI) and 24.65 % (PenAAc), significantly surpassing the control device (22.84 %). Moreover, hysteresis index is reduced from 4.20 % (control) to 0.33 % (5-AVAI) and 0.08 % (PenAAc). Additionally, the modified devices also demonstrated enhanced environmental stability across humidity, light, and thermal stress conditions.
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