Recent advances in UV photodetectors based on 2D materials: a review

Since the discovery of graphene there has been a strong interest in two-dimensional (2D) materials among the scientific community due to their extraordinary properties. Although ultraviolet (UV) photodetectors based on bulk wide bandgap semiconductors exhibit a good response, their photodetection performance significantly diminishes as their thickness is reduced to atomic scale, due to poor absorption and surface dangling bonds. 2D layered materials are free of dangling bonds and have a layer-dependent tunable bandgap and optoelectronic properties. Even an atomically thin layer of a 2D material shows high absorption due to strong light-matter interaction. 2D materials are attracting a lot of attention due to their compatibility with flexible, wearable devices and the ease of making van der Waals heterostructures. Although graphene and transition metal dichalcogenides have shorter band gaps, these materials can be easily integrated with other wide bandgap materials for UV detection, and such integration has often produced extraordinary device performance. Also, low bandgap, strong UV-absorbing 2D materials can be utilised for UV detection by using an optical bandpass filter. Recently, wide-bandgap 2D materials such as gallium sulphide (GaS), hexagonal boron nitride (hBN), and bismuth oxychlorides (BiOCls) have been explored for application in UV photodetection. Many of these wide bandgap materials show extraordinary UV photodetection performance.