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

Abstract 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.