Composition-Tunable Bandgap Engineering of Horizontally Guided CdS_xSe_1-x Nanowalls for High-Performance Photodetectors

Composition-adjustable semiconductor nanomaterials have garnered significant attention due to their controllable bandgaps and electronic structures, providing alternative opportunities to regulate photoelectric properties and develop the corresponding multifunction optoelectronic devices. Nevertheless, the large-scale integration of semiconductor nanomaterials into practical devices remains challenging. Here, we report a synthesis strategy for the well-aligned horizontal CdS_xSe_1-x (x = 0-1) nanowall arrays, which are guided grown on an annealed M-plane sapphire using chemical vapor deposition (CVD) approaches. Microstructural characterizations demonstrate these structures as horizontally guided nanowalls with high-quality crystallinity. Microphotoluminescence (μ-PL) reveals the CdS_xSe_1-x nanowalls exhibiting continuously tunable spontaneous emissions from 509 nm (pure CdS) to 713 nm (pure CdSe), further confirming that CdS_xSe_1-x alloys have a continuously tunable bandgap. Notably, a photodetector based on CdS_xSe_1-x nanowalls displays excellent photoelectric performance, such as high responsivity (3 × 10² ∼ 1 × 10³ A/W), high external quantum efficiency (1.01 × 10³ ∼ 2.93 × 10³), and fast response speed in the millisecond magnitude. Furthermore, the CdS nanowall-based photodetectors exhibit a remarkable image-sensing capability, indicating potential applications in high-performance image sensing in the future. Bandgap continuously tunable nanowall arrays with high-quality crystallinity inject great vitality into the manufacturing of high-performance integrated optoelectronic devices.