Strong Dual-Functional Enhancement in Flexible Photodetection and Photovoltaics of Two-Dimensional Large-Area WS

Two-dimensional (2D) material-based heterolayers (HLs) are very useful for flexible optoelectronic device applications due to their unique properties, but their performance is still limited due to the high dark current (DC) and poor quantum efficiency, mostly resulting from the interface properties at the heterojunction, including the low energy barrier. One promising method to reduce DC is to locate a high-bandgap, low-dimensional interlayer at the heterojunction interface as a blocking barrier. Here, we report dual-functional enhancement in flexible photodetection and photovoltaics of two-dimensional large-area WS2/MoS2 HLs by using a hexagonal boron nitride (h-BN) interlayer. The use of h-BN makes it difficult for the carriers to go over the energy barrier as well as for the photogenerated electrons and holes to be recombined at the interface, thereby reducing DC and facilitating the flow of the photocarriers, respectively. These effects remarkably enhance the photoresponse and energy harvesting. In particular, the specific detectivity increases ∼10 times at zero bias, i.e., under self-powered, and the photovoltaic power-conversion efficiency becomes almost doubled. The device shows excellent flexible stability by maintaining 76 and 54% of its original photocurrent (PC) and DC, respectively, despite 5000-bending cycles bending tests. The PC and DC also remain nearly unchanged for up to 750 h under ambient conditions, suggesting the excellent long-term stability of the device. These results suggest that all-2D WS2/h-BN/MoS2 HLs are very promising for applications in self-powered and/or energy-harvesting multifunctional optoelectronic devices.