Thermally Induced Anti‐Aggregation Evolution of Thick Bulk‐Heterojunction for vis–NIR Organic Photodetectors

Abstract Visible‐to‐near‐infrared organic photodetectors (vis–NIR OPDs) are highly desired due to their potential applications in both scientific research and industry. To develop state‐of‐the‐art diode‐type OPDs, general strategies aiming to reduce the dark current density (J_d) involve reducing the thickness of the bulk‐heterojunction (BHJ) active layer, but this simultaneously leads to a sharp drop in photoresponse. Herein, a facile fabrication strategy, i.e., thermally induced anti‐aggregation (TIAA) evolution strategy, is introduced for manipulating the phase separation scale and molecular arrangement orientation of the PBDB‐T:Y6 based active layer. To a typical 500 nm‐thick BHJ, much higher and balanced electron/hole mobilities are achieved through the TIAA manipulation. By effectively equilibrating the J_d (8.7 × 10^‐8 A cm^‐2) and responsibility (0.5 A W‐¹ at 860 nm), the optimized vis–NIR OPD showcases high specific detection of over 10¹² Jones (380–940 nm) and capability of faint IR light detection (≈10^‐10 W cm^‐2 at 850 nm) at −0.5 V bias. Meanwhile, the device displays the ability to monitor pulse signal in real time through photoplethysmography, indicating the potential of TIAA evolution strategy to fabricate high‐performance vis–NIR OPDs for next‐generation wearable health monitoring.