In Situ Condensation Passivation of Organosilane Cross-Linker Enables Inverted Organic Solar Cells near 19% Efficiency

Inverted organic solar cells (OSCs) exhibit excellent stability, making them promising candidates for practical photovoltaic applications. However, the power conversion efficiency (PCE) of inverted devices still falls behind that of conventionally structured OSCs. In this work, a practical strategy for enhancing inverted device performance is demonstrated by introducing an organosilane-based passivation layer onto the ZnO transport layer via solution processing and thermal cross-linking. During the in situ hydrolysis and condensation process, organosilanes can interact with the oxygen vacancy on the ZnO film to form Zn-O-Si bonds, thereby substantially reducing the surface defects of the ZnO film. Meanwhile, the Si-O-Si network structure formed by the condensation of organosilanes effectively improves hydrophobicity of the interface between ZnO and the active layer, thereby enhancing the stability of the device. When vinyltrimethoxysilane (VTMS) is employed as the passivation layer, the inverted OSCs based on the PM6: BTP-eC9 system achieve a maximum PCE of 18.92%. Furthermore, the VTMS/ZnO-based devices exhibited outstanding stability, owing to the suppressed photocatalytic activity of the ZnO film and the enhanced interfacial hydrophobicity induced by the Si-O-Si network formed through organosilane cross-linking. Following 4224 h of storage in a nitrogen-filled glovebox, the optimized device based on VTMS/ZnO retains 97.42% of its initial PCE. After 330 h of UV exposure, the optimized device could still maintains 91.06% of its initial PCE. These results demonstrate that this method holds great potential for practical applications in high-efficiency and stable inverted OSCs.