Dual-Channel Förster Resonance Energy Transfer Boosting Exciton Utilization Efficiency for High-Performance Layer-by-Layer Processed All-Small-Molecule Organic Solar Cells

All-small-molecule organic solar cells (ASM-OSCs) hold great potential for commercialization owing to their well-defined molecular structures and minimal batch-to-batch variations. Nevertheless, the inherent challenges in precise control of blend morphology of the active layer restrict exciton utilization efficiency, resulting in the restricted power conversion efficiencies (PCEs) in ASM-OSC compared with polymer-based OSCs. Herein, small molecule donor Por-BR is incorporated into the acceptor layer of the DAPor-DPP/6TIC system utilizing a layer-by-layer (LbL) deposition strategy to construct high-performance ASM-OSCs. The LbL deposition strategy facilitates the formation of a more pronounced vertical phase distribution in the active layer. Besides, dual-channel FRET from Por-BR to both DAPor-DPP and 6TIC occurs in the active layer. Benefiting from the combined advantages of the LbL deposition strategy and dual-channel FRET, a broader spatial distribution of exciton generation sites is achieved, accompanied by significantly improved exciton utilization efficiency, enhanced carrier mobility, and reduced charge recombination. The optimal device delivers a remarkable PCE of 17.76%, representing one of the highest PCE values reported so far in ASM-OSCs. This work offers an effective strategy for device performance enhancement, which in turn facilitates the industrialization of OSCs.