Fig. 1. UV spectral region and its subdivisions

Fig. 2. Schematics of ultraviolet photodetectors based on narrow bandgap semiconductor nanostructures

Fig. 3. Absorption and ultraviolet photodetection application of horizontal Si nanowires^［31-32］

Fig. 4. Absorption and ultraviolet photodetection application of vertical Si nanowires array^{［35，37］}

Fig. 5. UV photodetectors based on ultrathin film of narrow bandgap inorganic semiconductors^［40-42］

Fig. 6. UV photodetectors based on ultrathin nanosheet of narrow bandgap perovskite materials^［47-48］

Fig. 7. UV photodetectors based on 2D layered semiconductors with narrow bandgap^{［52，54，56］}