Interfacial Electric Field-Modulated Broadband Self-Powered Photodetection Enabled by Plasmonic Semiconductor Heterojunction Films

The interfacial electric field (IEF) in semiconductor heterojunctions plays a vital role in self-powered photodetection. However, effectively modulating the IEF to enhance broadband photodetection in single heterojunctions remains a significant challenge. In this study, we present a strategy for IEF-modulated broadband self-powered photodetection using a plasmonic W18O49/TiO2 heterojunction film. The film is fabricated through the solvothermal growth of W18O49 nanowires on TiO2 nanorod arrays. By applying external voltage treatment, we demonstrate the ability to tune the Fermi level of the plasmonic W18O49 component, which in turn modulates the IEF at the W18O49/TiO2 heterojunction. The enhanced IEF facilitates both the separation of interband-excited electron–hole pairs and the ultrafast transfer of IR-excited plasmonic hot electrons. Notably, compared with 0 V and −2 V treatments, the +2 V-treated heterojunction film exhibits a remarkable ∼2.9-fold and ∼4.5-fold enhancement in 365 nm responsivity (598.6 μA/W), respectively. Additionally, the 0 V-treated film shows a ∼3.2-fold higher 940 nm responsivity than the −2 V-treated counterpart. In contrast, single-component films exhibit negligible responses, confirming the essential role of the IEF in enabling self-powered UV-to-NIR broadband photodetection. This work offers a promising approach for achieving high-performance optoelectronics by modulating the IEF in semiconductor heterojunctions.