UV‐Vis‐NIR Broadband Bi 2 S 3 /SnO 2 /p‐Si Heterojunction Photodetector with High Switching Ratio and Fast Response

Recently, SnO 2 has emerged as a promising core material for low‐cost, high‐performance photodetectors due to its excellent comprehensive properties. However, its narrow spectral response range limits its application in broadband detection. In this study, Bi 2 S 3 nanorods were fabricated for the first time via a sol‐gel method on a SnO 2 thin film, constructing a Bi 2 S 3 /SnO 2 /p‐Si (BSS) heterojunction photodetector. The structural and morphological characteristics of the BSS heterojunction were examined using X‐ray diffraction and scanning electron microscopy. Optical and electronic spectral analyses (absorption spectroscopy and ultraviolet photoelectron spectroscopy) confirmed that the BSS formed a well‐defined vertical heterostructure, enabling the device to detect UV‐Vis‐NIR light spanning 365‐1305 nm. At a 5 V bias under 780 nm light, the BSS heterojunction photodetector exhibited a high switching ratio of 2.19 × 10 4 , a rapid decay time of 28.86 ms, a responsivity of 2.21 A/W, and a specific detectivity of 3.92 × 10 12 Jones. Band alignment analysis shows a type‐II (Bi 2 S 3 /SnO 2 ) and a type‐I (SnO 2 /p‐Si) alignment, respectively, thus providing an effective band structure for efficient carrier separation and recombination suppression. This work demonstrates the significant potential of the high‐performance SnO 2 ‐based heterojunction photodetector for broadband detection applications.