Suppression of Photo‐Mediated Traps in Integrated Organic Photovoltaic–Photodetector Devices via N‐Type Self‐Assembly‐Driven Interfacial Engineering

Abstract Integrated organic photodetector‐photovoltaics (OPD‐OPVs) combine energy harvesting and photodetection, facilitating the development of self‐sustaining sensors. The electron transport layers (ETLs) of these devices are critical for regulating the charge‐transport dynamics across both functions. ZnO, a conventional ETL material offering efficient charge extraction, suffers critical instability issues (photocatalytic degradation of organics), leading to increased defect‐mediated leakages, severely limiting its commercialization. To address the scarcity of alternatives to ZnO ETLs, a molecularly engineered, n‐type, self‐assembled monolayer (SAM)‐based ETL, ((3‐(1,3‐dioxoisoindolin‐2‐yl)propyl)phosphonic acid) (3‐PAPh), is developed. 3‐PAPh chemisorbs onto the electrode, a process that templates a structurally ordered morphology, wherein the resulting 3‐PAPh reduces the interfacial trap density and establishes a high activation energy barrier, fundamentally suppressing the parasitic leakage currents. A PM6:Y6‐based device employing this synergistic ETL yielded a record‐low noise current (7.65 fA at V → 0 V) and high measured specific detectivity (1.03 × 10 13 cm Hz 0.5 W −1 at 808 nm and bandwidth = 1 Hz) in self‐powered OPD mode, while affording efficient indoor power generation (output power density = 74.4 µW cm −2 under LED 1000 lx (2700 K)) in OPV mode. The chemically inert interface prevented trap formation during operation, maintaining >87% power‐conversion efficiency after maximum power‐point tracking for 500 min.