The world's first homojunction UV light‐emitting diode (LED) based on both p‐type and n‐type ZnO nanoparticles (NPs) is demonstrated. Nitrogen‐doped ZnO and gallium‐doped ZnO NPs are provided to fabricate p‐type and n‐type NP layers, respectively. The LEDs with the structures of p‐ZnO/GZO and p‐ZnO/n‐ZnO/GZO are fabricated. These devices show near UV electroluminescence (EL) at room temperature and emission power doubled by inserting the n‐ZnO NP layer. By comparing the results of I–V, EL and photoluminescence for LEDs, it can be confirmed that the holes inject from p‐ZnO NP layer to n‐ZnO NP layer and the mechanism of these devices are that of p‐n junction LEDs.

In this work, nitrogen-doped ZnO nanoparticles were synthesized in various conditions by the gas evaporation method with DC arc plasma. Nitrogen concentrations of 6.38 × 1018 cm−3 to 2.6 × 1019 cm−3 were obtained at a chamber pressure of 150 torr, using arc currents of 20 A to 70 A. The intensities of local vibrational modes at 275 cm−1 and 581 cm−1 in the Raman spectra of ZnO nanoparticles showed a dependency on the nitrogen concentration in the ZnO nanoparticles. The ratios of donor–acceptor pair and exciton emissions in the photoluminescence spectra of nitrogen-doped ZnO nanoparticles, and the electroluminescence of light-emitting diodes based on these nanoparticles, were nearly proportional to the Raman peak’s intensity at 275 cm−1. The results indicated that the nitrogen dopants in the ZnO nanoparticles were acting as an acceptor.

The fabrication of ZnO nanoparticles (NPs) was monitored and studied in situ by controlling the plasma parameters of the direct current (DC) arc plasma system, such as the current density and chamber pressure. The optical emission signature of nitrogen was spectroscopically studied using optical emission spectroscopy (OES) techniques, and it showed a dependency on the nitrogen concentration in the ZnO nanoparticles in relation to the output of the ZnO NPs-based homojunction light-emitting diodes (LEDs). The synthesized NPs had a good crystalline quality and hexagonal wurtzite structure, and they were characterized by X-ray diffraction (XRD) techniques and scanning electron microscope (SEM). The photoluminescence properties of the ZnO NPs and the optical and electrical parameters of the LEDs were also analyzed and correlated. The results indicate that the nitrogen dopants act as acceptors in the ZnO NPs and are favored in low plasma temperatures during fabrication. We anticipate that the results can provide an effective way to realize reliable nitrogen-doped p-type ZnO and tremendously encourage the development of low-dimensional ZnO homojunction LEDs.