A Design Strategy for Low‐Cost Single/Dual‐Band Photodetector: Bulk Heterojunction and Interface Engineering

Abstract Photodetectors (PDs) with band selection functions are highly desirable for the future complex environment. Currently, band‐selective PDs are typically realized by integrating various optical filters with broadband PDs or constructing heterojunction with multi‐photo‐absorbing layers. However, these methods cause increased manufacturing costs and device integration complexity. Here, a novel solution‐processed perovskite bulk heterojunction (BHJ) layer (MAPbI 3 :MA 3 Bi 2 I 9 ) is developed as photo‐absorbing layer, and an effective interface engineering is proposed to selectively shield photo‐generated carriers in the BHJ. By regulating the bias voltage, the tunneling probability of photo‐generated carrier of MAPbI 3 in the BHJ layer can be easily controlled, enabling band‐selective capability. The PD exhibits a superior photo‐response in the visible and near‐infrared region at the −0.3 V, with responsivity of 26.5 and 70.2 mA W −1 for 500 and 740 nm, respectively. But, at the 0.1 V, the PD responds only to the visible region with a photo‐response of 3.7 mA W −1 (500 nm) and maintains a high rejection ratio ( R 500 nm / R 740 nm ) of 28.5. This PD also exhibits a fast response speed (rise time: 220 µs, fall time: 240 µs). This work provides a novel strategy to fabricate a cost‐effective multifunctional photodetector for future advanced optoelectronic system.