Band engineering to suppress dark current in self-powered solar-blind photodetectors for optoelectronics in harsh environments

Solar-blind ultraviolet (UV) communication has gained significant attention due to its low background noise, non-line-of-sight transmission, and high security. Achieving efficient solar-blind UV communication requires photodetectors with high sensitivity to weak solar-blind UV signals, low dark current, and excellent stability. In this study, an all-inorganic \ensuremath{\beta}-${\mathrm{Ga}}_{2}{\mathrm{O}}_{3}/\mathrm{Cu}\mathrm{O}/\mathrm{Ni}\mathrm{O}$ three-layer heterostructure was developed for self-powered solar-blind UV photodetectors. The introduction of a $\mathrm{Cu}\mathrm{O}$ electron-blocking layer effectively suppressed thermal carrier transport in the dark by creating a high conduction-band barrier, significantly reducing dark current. Compared to traditional \ensuremath{\beta}-${\mathrm{Ga}}_{2}{\mathrm{O}}_{3}/$p-$\mathrm{Ni}\mathrm{O}$ two-layer heterojunctions, the dark current of the \ensuremath{\beta}-${\mathrm{Ga}}_{2}{\mathrm{O}}_{3}/\mathrm{Cu}\mathrm{O}/\mathrm{Ni}\mathrm{O}$ photodetector is reduced by factors of 5.9 at 0 V and 19.2 at 20 V, respectively, along with a 77.6-fold and 5.9-fold increase in the photocurrent-to-dark current ratio. The device demonstrated a responsivity of 0.27 A/W under 254-nm illumination with a light power of 100 nW/${\mathrm{cm}}^{2}$ and robust stability across extreme temperatures (\ensuremath{-}170 \ifmmode^\circ\else\textdegree\fi{}C to 100 \ifmmode^\circ\else\textdegree\fi{}C). These results highlight the potential of the \ensuremath{\beta}-${\mathrm{Ga}}_{2}{\mathrm{O}}_{3}/\mathrm{Cu}\mathrm{O}/\mathrm{Ni}\mathrm{O}$-based photodetector for high-performance solar-blind UV communication systems.