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

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 (MAPbI₃:MA₃Bi₂I₉) 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 MAPbI₃ 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.