Bilateral coordination interfaces enable long-term stable organic solar cells under multiple stress conditions

Abstract

Achieving long-term operational stability alongside high power conversion efficiency remains one of the most critical challenges for organic solar cells (OSCs), as interfacial degradation under heat, humidity, and continuous illumination severely limits device lifetime. Although many studies report improved stability under individual stress conditions, few OSC studies have demonstrated extended durability across multiple stress conditions. Here, we report a bilateral bilayer interface engineering strategy centered on a novel coordination-engineered cathode stabilization material, Cu-bathocuproine (BCP), formed by coordinating Cu with conventional BCP. Introduced as an overlayer on aliphatic amine-functionalized perylene-diimide (PDINN), Cu-BCP serves as an efficient electron-extraction interlayer and a chemically stabilized buffer that suppresses detrimental interfacial reactions with the non-fullerene acceptor. Combined with a self-assembled monolayer/metal oxide anode bilayer, [2-(9H-carbazol-9-yl)ethyl]phosphonic acid (2PACz)/MoO_x, OSCs with the structure of indium tin oxide (ITO)/PDINN/Cu-BCP/PM6:L8-BO:PC₇₁BM/2PACz/MoO_x/Ag achieve a power conversion efficiency of 16.70%, surpassing the reference devices based on PDINN (14.58%) and PDINN/BCP (15.05%). Importantly, the bilateral bilayer devices exhibit substantially enhanced durability under multiple independent stress conditions, retaining 80% of their initial efficiency after 1,200 h in air storage, 1,320 h at 65 °C/65% relative humidity, and 1,008 h under continuous 1-sun illumination, corresponding to the longest T₈₀ lifetime among PDINN-based devices. The improved stability is associated with suppressed trap-assisted recombination, reduced leakage current, and lower charge-transfer resistance. Moreover, large-area modules deliver an efficiency of 14.57% with a 54 cm² active area, indicating an 87% cell-to-module ratio. These results demonstrate that ultrathin stabilization-layer design within bilateral bilayer interfaces is an effective route toward efficient, stable, and scalable OSCs.

Keywords

Bilateral interface engineering / coordination-engineered cathode / self-assembled monolayer / operational stability

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