UV–Vis–NIR\nBroadband Self-Powered CuInS₂/SnO₂ Photodetectors\nand the Application in Encrypted\nOptical Communication

Abstract

Photodetectors\n(PDs) with broadband photoresponse can meet the\ndemand for multiband detection in complex environments, overcoming\nthe technological complexity issue of integrated narrow-band PDs.\nSelf-powered heterojunction PDs having ultraviolet–visible–near-infrared\nbroadband photoresponse were constructed by using SnO₂ nanopillars\nand CuInS₂ nanoflakes. The dimension, crystalline quality,\nand energy level structure of the SnO₂ nanopillars were\nregulated by changing the concentration of Sn ions in the precursor\nsolution. The optimized interfacial energy band structure of the heterojunction\ncan increase the transfer ability of the photogenerated carrier. The\noptimum performance is achieved for the CuInS₂/SnO₂(0.025M) PD prepared at 0.025 M Sn ion concentration in the\nprecursor solution with the responsivities of 1.15, 6.13, and 1.02\nmA/W, and detectivities of 1.19 × 10¹⁰, 6.35 ×\n10¹⁰, and 1.02 × 10¹⁰ Jones under 254 nm\nsolar-blind ultraviolet light, 475 nm visible light, and 940 nm near-infrared\nlight. Furthermore, a proof-of-concept solar-blind ultraviolet–visible–near-infrared\nencrypted communication system utilizing a broadband self-powered\nCuInS₂/SnO₂ PD as the receiving terminal and\nsolar-blind ultraviolet light, ultraviolet light, visible light, and\nnear-infrared light as the carrier and encryption protocol is proposed.\nThe PD has great potential for applications in the field of encrypted\noptical communication.