Bias-Tolerant Responsivity and Noise Suppression via Ternary Nano-modulation for Multi-functional Organic Photodiodes

Abstract Organic photodetectors based on binary bulk heterojunctions (BHJs) are widely used because of their high efficiency, yet they face limitations in maintaining stable operation under reverse bias. In this study, the non-fullerene acceptor BTP-eC9 is employed in a ternary BHJ to establish a stable nanoscale molecular arrangement and enable reliable photodetection under reverse-bias-induced electric-field stress. Introducing a PM6:BTP-eC9:Y12 ternary BHJ tunes the energy levels, resulting in suppressed dark current and reliable responsivity of 0.56 A W–1 at –2 V. Compared with binary-based photodetectors, the ternary devices show substantially smaller variations in low-frequency noise with applied bias. This advantage of the ternary architecture is retained in both conventional and inverted device configurations. Notably, the ternary device sustains clear photoplethysmography signals at –3 V and supports sensing capability in a flexible device. These results demonstrate ternary nanoscale modulation as an effective strategy for reliable multi-functional photodetection.