Thieno[3,4-b]pyrazine-containing D-A conjugated polymer-based photodetectors with high performance and UV–visible dual-band response for color temperature sensor and encrypted optical communication

Abstract

Three thieno[3,4-b]pyrazine (TP)-containing D-A type conjugated polymers are successfully used to develop multifunctional high-performance organic photodetectors (OPDs). The TP acceptor units are respectively coupled with three different donor units to effectively regulate their molecular energy levels and carrier mobilities. The resultant polymers exhibit dual-band absorbance in the UV–visible region, intramolecular charge transfer (ICT) effect and efficient ambipolar transport characteristics. They are evaluated as the single photosensitive layers in OPDs for the first time. The optimal device based on TP-Si presents a peak external quantum efficiency (EQE) over 40% and a high specific detectivity (D∗) of 3.35×1012 Jones with fast temporal response under 560 nm at −1.5 V, which are superior to the most of reported single-active-layer OPDs. The high performance could be ascribed to the well-balanced photogenerated carriers and the efficient charge separation and transport in the device. Noteworthy, this dual-band response device can be used as a novel color temperature (CT) sensor for complementary white light illumination, and an encrypted UV–visible light communication scheme has been successfully demonstrated. The results show that these ambipolar D-A polymers have a broad application prospect in secure optical communication in the future.