Record-High Responsivity and Detectivity of a Flexible Deep-Ultraviolet Photodetector Based on Solid State-Assisted Synthesized hBN Nanosheets

Till date, all reports on hexagonal boron nitride (hBN)-based deep-ultraviolet (DUV) detectors are on rigid substrates with a moderate photoresponse, which limits their utility in flexible electronics-related applications. Herein, we report two-dimensional (2D) hBN on a copper (Cu)-based flexible DUV detector with very high photoresponsivity and external quantum efficiency (EQE). High-purity 2D hBN nanosheets were synthesized by a one-step solid-state reaction and drop-casted onto Cu(111), making the device fabrication process facile, simple, and low-cost. Detailed structural and chemical characterization studies reveal the formation of few layered, hexagonal phased boron nitride nanosheets. Schottky junction-based metal–semiconductor contact configuration is used to obtain hot-carrier reflections on the metal side (Cu), which leads to enhanced quantum efficiency of the photodetector. The as-fabricated DUV photodetector exhibits a responsivity of 5.022 A/W, a quantum yield of 2945%, and a specific detectivity of 6.1 × 1012 Jones at a power intensity of 9.937 μW/cm2, which are 2–3 orders higher than the values reported for other hBN-based photodetectors. This enhanced performance can be attributed to the UV light-modulated band–band excitation of hBN nanosheets and internal photoemission due to the hBN/Cu Schottky junction. The device shows a fast response speed of 0.2 s and a remarkable stability over 500 cycles of continuous bending. This strategy of using 2D nanosheets/metal provides a scope of fabricating low-cost, high-performance, flexible DUV photodetectors for various optoelectronic devices and security applications.