Figure 4.

Heterojunction LED structure and light emission of LED. (a) The schematic diagram of the heterojunction LED structure and (b) the photography of the light emission of LED under forward bias at the dark room.
n-ZnO NRs in this heterojunction light emitting diode was annealed in nitrogen ambient
at 200°C. Light emissions of all the samples in this study were observed by naked
eyes in the dark room.