Observing Charge Transfer Interaction in CuI and MoS2 Heterojunction for Photoresponsive Device Application

Charge transfer interaction at the interface of semiconducting layered materials is of great interest to develop effective heterojunction optoelectronic devices. Here, we demonstrate the charge transfer interaction and formation of an active heterojunction between the molybdenum disulfide (MoS2) layer and p-type copper iodide (CuI) exhibiting excellent photoresponsive properties. The CuI film was fabricated by solid phase iodization of a copper film and direct thermal evaporation processes, which led to the formation of a transparent conducting layer. The thermally evaporated CuI film showed the main diffraction peak for the (111) plane, confirming the formation of the γ-CuI cubic crystal structure along the (111) plane on the MoS2 layers. The photoluminescence (PL) quenching effect was observed for the γ-CuI/MoS2 heterostructure, which can be attributed to the spontaneous separation of charge carriers at the interface. A photoresponsivity of 0.27 A/W was obtained at a bias voltage of 5 V for the γ-CuI/MoS2 heterojunction device with illumination of monochromatic light. Our finding shows that the excellent photoresponsivity in the fabricated heterojunction is due to the formation of an effective interface between the two materials for efficient exciton dissociation and charge separation.