Efficient Non‐Fullerene Acceptor‐Based Organic Photodetectors Achieved by Reduced Deep Traps in Highly Intermixed Co‐Evaporated Bulk‐Heterojunction Blends

Organic photodetectors (OPDs) based on co‐evaporated bulk heterojunctions (BHJs) have demonstrated their potential for industrially relevant fabrication of high‐efficiency devices. However, acceptor materials choice is still dominated by fullerenes, which show sub‐optimal performance due to deep trap states originating from unfavorable BHJ morphology. Herein, the non‐fullerene acceptor Cl 6 ‐SubPc is used to replace C 60 in 2‐((8‐methyl‐8H‐thieno[2,3‐b]indol‐2‐yl)methylene)−1H‐cyclopenta[b]naphtha‐lene‐1,3(2H)‐dione (MPTA):C 60 BHJs. Through active layer thickness tuning, the effective Cl 6 ‐SubPc intercalation into MPTA domains is achieved for a highly intermixed BHJ morphology. This results in a high yield of interfacial charge‐transfer states, which are readily quenched under electric field for efficient OPD photoresponse. In comparison to C 60 ‐based devices, Cl 6 ‐SubPc suppresses the residual MPTA aggregation and the adduct generation with MPTA, preventing deep‐trap state formation. As such, non‐fullerene acceptor‐based OPDs are highly promising for trap‐free photodetection, enabling superior performances under low‐light illumination.