3D Heterojunction of t-Se Encapsulated SnS ₂ Nanoflower Arrays for Broadband Self-Powered Photodetection

Improving the zero-bias photocurrent density of the photoelectrochemical (PEC) photodetector boosts its responsivity and aids in developing portable, low-energy-consumption devices. Constructing a high-quality heterojunction facilitates the separation and transport of photogenerated carriers, playing a crucial role in enhancing photocurrent density. In this work, a three-dimensional (3D) heterojunction of t-Se-coated SnS 2 nanoflower arrays was successfully constructed via a simple hydrothermal approach followed by electrochemical deposition. When serving as a photoelectrode for the PEC photodetector, it significantly boosts the photocurrent density and the responsivity. Under white light illumination (258.0 mW/cm 2 ), the photocurrent density achieves 1 mA/cm 2, which is 13.3 times and 200 times that achieved when individual t-Se films and SnS 2 nanosheet arrays were employed, respectively. At the optimal response wavelengths (400 nm for SnS 2 and 600 nm for t-Se), the responsivity is enhanced by factors of 6.3 and 65.7. A broadband (400∼900 nm) and rapid photoresponse is demonstrated, with the response time less than 40 ms. Type II energy band alignment between SnS 2 and t-Se, along with the unique morphology of the 3D heterojunction, significantly contributes to the enhanced performance of the device.