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

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.