High-responsivity broadband photodetection of an ultra-thin In₂S₃/CIGS heterojunction on steel

Cu(In, Ga)Se₂ (CIGS) is a promising light harvesting material for large-area broadband photodetection, but it has been rarely studied up to now. Here an In₂S₃/CIGS heterojunction photodiode on steel is shown to be highly broadband photo-sensitive, with a photoresponsivity over 0.8 A/W, an external quantum efficiency over 100%, and a detectivity over 8×10¹⁰ Jones from 505 to 910nm under a reverse bias of 1 V. Moreover, the CIGS photodiode exhibits an outstanding weak light detection ability (i.e., at light power density of 20 µW/cm²), reaching a record responsivity of 2.06 A/W, an impressive EQE of 293%, and a good detectivity of 2.3 × 10¹¹ Jones at 870 nm under 1 V reverse bias. Importantly, the CIGS photodiode, working as a self-powered photodetector, under 0 V, shows a record detectivity of ∼3.4 × 10¹² Jones with a high responsivity of ∼0.44 A/W and a high EQE of ∼63%, at 870 nm.