High-performance dual-mode ultra-thin broadband CdS/CIGS heterojunction photodetector on steel

An ultra-thin CdS/CIGS heterojunction photodiode fabricated on steel firstly exhibits dual-mode broadband photodetection from ultraviolet to near infrared spectrum. In the photovoltaic mode, the CIGS photodiode, working as a self-driven photodetector, shows an outstanding photodetection capability (under a light power density of 20 mu W cm(-2) at 680 nm), reaching a record detectivity of similar to 4.4x10(12) Jones, a low noise equivalent power (NEP) of 0.16 pW Hz(-1/2) and a high I-light/I-dark ratio of similar to 10(3), but a relatively low responsivity of similar to 0.39 A W-1 and an external quantum efficiency (EQE) of similar to 71%. Working under the same illumination but in the photoconductive mode (1 V reverse bias), the responsivity and EQE are significantly enhanced to 1.24 A W-1 and 226%, respectively, but with a relatively low detectivity of 7x10(10) Jones and a higher NEP of 10.1 pW Hz(-1/2). To explain these results, a corrected photoconductive gain (G) model indicates that minority electrons could be localized in the defects, surface states and depletion region of the CIGS photodiode, causing excess hole accumulation in the ultra-thin CIGS photodiode and thus high EQE over 100% (G over 1). (C) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

Automated summary

An ultra-thin CdS/CIGS heterojunction photodiode fabricated on steel demonstrates dual-mode broadband photodetection. In the photovoltaic mode, the CIGS photodiode shows outstanding photodetection capability, while in the photoconductive mode, the responsivity and EQE are significantly enhanced.