Composition-Tunable\nBandgap Engineering of Horizontally\nGuided CdS<sub><i>x</i></sub>Se<sub>1–<i>x</i></sub> Nanowalls for High-Performance Photodetectors

Composition-adjustable semiconductor nanomaterials have\ngarnered\nsignificant attention due to their controllable bandgaps and electronic\nstructures, providing alternative opportunities to regulate photoelectric\nproperties and develop the corresponding multifunction optoelectronic\ndevices. Nevertheless, the large-scale integration of semiconductor\nnanomaterials into practical devices remains challenging. Here, we\nreport a synthesis strategy for the well-aligned horizontal CdS<sub><i>x</i></sub>Se<sub>1–<i>x</i></sub> (<i>x</i> = 0–1) nanowall arrays, which are guided grown\non an annealed M-plane sapphire using chemical vapor deposition (CVD)\napproaches. Microstructural characterizations demonstrate these structures\nas horizontally guided nanowalls with high-quality crystallinity.\nMicrophotoluminescence (μ-PL) reveals the CdS<sub><i>x</i></sub>Se<sub>1–<i>x</i></sub> nanowalls exhibiting\ncontinuously tunable spontaneous emissions from 509 nm (pure CdS)\nto 713 nm (pure CdSe), further confirming that CdS<sub><i>x</i></sub>Se<sub>1–<i>x</i></sub> alloys have a continuously\ntunable bandgap. Notably, a photodetector based on CdS<sub><i>x</i></sub>Se<sub>1–<i>x</i></sub> nanowalls\ndisplays excellent photoelectric performance, such as high responsivity\n(3 × 10<sup>2</sup> ∼ 1 × 10<sup>3</sup> A/W), high\nexternal quantum efficiency (1.01 × 10<sup>3</sup> ∼ 2.93\n× 10<sup>3</sup>), and fast response speed in the millisecond\nmagnitude. Furthermore, the CdS nanowall-based photodetectors exhibit\na remarkable image-sensing capability, indicating potential applications\nin high-performance image sensing in the future. Bandgap continuously\ntunable nanowall arrays with high-quality crystallinity inject great\nvitality into the manufacturing of high-performance integrated optoelectronic\ndevices.