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 W 18 O 49 /TiO 2 heterojunction film. The film is fabricated through the solvothermal growth of W 18 O 49 nanowires on TiO 2 nanorod arrays. By applying external voltage treatment, we demonstrate the ability to tune the Fermi level of the plasmonic W 18 O 49 component, which in turn modulates the IEF at the W 18 O 49 /TiO 2 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.