Insight into the Optoelectronic Response of Exfoliated Bi₂Te₃–PEDOT:PSS/SnS Heterostructure-Based Self Powered Vis-NIR Photodetector

Multispectral photodetectors are essential for diverse applications such as machine vision, quantum computing, and wafer inspection. Conventional detectors often rely on epitaxially grown materials such as Si and InGaAs, which involve complex fabrication processes. In this study, we present a self-powered Vis-NIR photodetector based on a hybrid bulk heterostructure of SnS–Bi2Te3–PEDOT:PSS, fabricated entirely through solution-based techniques. A spray-pyrolyzed SnS film serves as the photoactive layer onto which exfoliated Bi2Te3 integrated with PEDOT:PSS is deposited, forming a vertical heterojunction. Structural analysis via X-ray diffraction and Raman techniques confirms the successful formation of SnS and Exfoliated Bismuth Telluride. Optical studies reveal enhanced absorption in the near-infrared (NIR) region. Bi2Te3, an ultranarrow bandgap semiconductor (Eg ∼ 0.15 eV), and SnS, a narrow bandgap (Eg ∼ 1.0 eV) layered semiconductor, offer strong light absorption in the visible and NIR ranges. The device demonstrates a spectral response from Visible to NIR, with a peak responsivity of 3.78 mA/W and a fast response time of 86 ms at zero bias. Mechanistic studies indicate that the photothermoelectric effect from Bi2Te3 and PEDOT:PSS enhances the NIR response, while SnS contributes predominantly through photovoltaic effect in the visible range, aided by efficient hole transport from PEDOT:PSS. The detector maintains high stability over >500 photocycles and offers a facile route to scalable, low-cost multispectral photodetection. This work provides critical insight into the interplay between photovoltaic and photothermoelectric effects in hybrid heterostructures and highlights the potential of Bi2Te3-based detectors for ambient light sensing and photonic applications.