Ultraviolet light emitting diode based on p-NiO/n-ZnO nanowire heterojunction

We fabricated nanowire-based ultraviolet (UV) light emitting diodes (LEDs) consisting of ITO/p-NiO/n-ZnO nanowires/AZO/n-Si heterostructure by using a dimensional transition technique of 1D to 2D. The p-type NiO layer was directly deposited on the ZnO nanowire arrays, followed by the growth of ITO electrode, resulting in the full coverage of the top surface of the ZnO nanowires and their electrical interconnection. The current–voltage curve of the LED showed obvious rectifying characteristics with a threshold voltage of about 8V and low leakage current. Under forward bias, this device exhibited UV electroluminescence located at around 380nm coming from band edge transition of the ZnO and the broad visible emission peak around 450–650nm was attributed to the n-ZnO defect level emission. The origin of the UV and visible emission were discussed in term of the energy band diagram of the p-NiO/n-ZnO nanowires heterjunctions. ► The n-ZnO nanowire based light emitting diodes were fabricated using p-NiO hole injection layer. ► The ZnO/NiO heterojunction showed obvious rectifying characteristics. ► This device exhibited strong UV and weak visible electroluminescence. ► The pure UV emission originated from the ZnO nanowires. ► We found that the p-NiO exhibited suitable p-type characteristics for hole injection.