Molecular Design of Oligomers for Codeposited Perovskite Solar Cells: Enabling Synergistic Control of Crystallization and Carrier Dynamics

Achieving high-efficiency, stable perovskite solar cells (PSCs) requires simultaneous control of film defects and buried interfaces. Here, we report a codeposition strategy using rationally designed 4PACz oligomers. Featuring multidirectional phosphate groups, these oligomers self-assemble to tune the substrate work function, facilitate charge transport, and guide crystallization while passivating defects. Specifically, tri-4PACz achieves an optimal balance between solubility and defect suppression. Consequently, tri-4PACz-based PSCs deliver efficiencies of 26.2% (0.098 cm2) and 22.2% (69.5 cm2 modules). Unencapsulated devices retain 98.7% of initial efficiency after 1000 h of illumination and 96.6% after 500 h at 85 °C. This strategy effectively resolves the trade-off between structural control and defect passivation, paving the way for high-performance, stable PSCs.