Bias-switchable dual-mode organic photodetectors and applications

Abstract

Organic photodetectors (OPDs) are emerging as versatile alternatives to traditional inorganic photodetectors, offering tunable optical properties, flexible architectures, and cost-effective, solution-processable fabrication. While single-band OPDs have been developed for specific spectral ranges, high-performance multispectral OPDs remain challenging. This work presents a bias-switchable dual-band OPD featuring a back-to-back stacked double bulk heterojunction structure. The front junction is sensitive to visible light, and the rear junction to near-infrared (NIR) light, enabling selective spectral response by controlling the applied bias polarity. Under forward bias, the device responds strongly to visible wavelengths. Under reverse bias, it selectively detects NIR light. The broadband photoresponse is achieved using duty cycled square-wave voltage operation. The dual-mode architecture reduces device complexity and enhances flexibility compared to conventional inorganic broadband photodetectors. With external quantum efficiencies of 50% at 630nm and 60% at 860nm, the OPD demonstrates high spectral selectivity and rapid response, making it suitable for advanced applications such as security monitoring, artificial intelligence, high-resolution imaging, and encrypted optical communication. This approach offers a promising solution for next-generation multispectral photodetection in compact, adaptive optoelectronic systems.