High-Speed, UV-NIR Dual-Band Photodetection via a 2H-MoSe₂/Si/1T-WS₂ Bipolar Heterojunction

Ultraviolet (UV) and near-infrared (NIR) dual-band photodetection is critical for applications ranging from secure optical communication and environmental monitoring to biomedical imaging. However, existing dual-band systems typically rely on discrete single-band detectors combined with optical filters, leading to complex alignment and high cost. Herein, we demonstrate a bipolar heterojunction (BHJ) based on a 2H-MoSe₂/Si/1T-WS₂ structure for filter-free, high-speed UV-NIR dual-band photodetection. The optimized device achieves high responsivities of 0.7 A/W@365 nm and 0.8 A/W@1064 nm at bias voltage of -2 V, along with a fast response time of 1.28 μs and a -3 dB bandwidth of 70 kHz. Furthermore, in comparative evaluations with broadband Si photodiodes, the BHJ successfully enabled high-quality NIR single-pixel imaging, reconstructing high-resolution images with 128 × 128 pixels under ambient lighting conditions. This work validates the potential of such transition metal dichalcogenides-Si heterojunctions for next-generation multispectral sensing and imaging systems.