Ultraviolet–Visible-Near-Infrared Broadband Photodetector Enabled by Cs₂AgBiBr₆: Sn/Conjugated Polymer Heterojunction

Broadband photodetectors covering ultraviolet (UV) to near-infrared (NIR) wavelengths play an essential role in communications, imaging, and biosensing. Developing a single photodetector with a broadband optical response operating at room temperature can significantly reduce the complexity and cost of receiver systems for multispectral applications. In this work, utilizing the porous structure characteristics of Cs₂AgBiBr₆:Sn thin films, a self-powered detector with broad spectral response (UV-vis-NIR) was achieved by constructing an effective Cs₂AgBiBr₆:Sn/PDPP3T heterojunction. This photodetector possesses a broad response spectrum from 350 to 950 nm with an average detection rate exceeding 10¹¹ Jones and maintains excellent photoelectric performance over two months. Sn²⁺ doping effectively reduces the bandgap of Cs₂AgBiBr₆, enhancing its near-infrared absorption and optimizing energy level alignment with conjugated polymer (diketopyrrolopyrrole-terthiophene, PDPP3T). More importantly, the porous structure derived from Sn doping significantly improves carrier extraction and transport under a near-infrared light response at the heterojunction interface. Utilizing its broad spectral response characteristics in the UV-vis-NIR range, a novel information transfer and encryption system employing full optical modulation has been realized within a single perovskite photodetector. This work provides a new approach to fabricating lead-free double perovskite broadband photodetectors with potential applications in photonic devices.