Fabrication of ZnO Nanorods p-n Homojunction Light-Emitting Diodes Using Ag Film as Self-Doping Source for p-Type ZnO Nanorods

In this study, homojunction light-emitting diodes (LEDs) based on n-type zinc oxide (ZnO) nanorods (NRs)/silver (Ag)-doped p-type ZnO NRs were successfully fabricated by low-temperature solution process. Here, the Ag thin film used as a template and dopant source for the growth of p-type ZnO NRs as well as a bottom electrode. The Ag-doped p-type ZnO NRs were synthesized using an ammonium hydroxide solution, which possesses a high pH value of 11.6 to dissolve the Ag film and form Ag⁺ ions in the solution. Using these Ag-doped p-type ZnO NRs as a template, n-type ZnO NRs were epitaxially grown on top of them at 90 °C to form ZnO NRs p-n homojunction. These ZnO NRs p-n homojunction LEDs showed a typical rectifying behavior with a turn-on voltage of 3.5 V and a high rectifying ratio of 1.5 × 10⁵ at 5 V. Furthermore, under a forward bias of 9 V, the LED exhibited a wide yellow electroluminescence emission centered at 645 nm, which was attributed to the various emission sites of ZnO deep-level defects. This study suggests a facile fabrication method for ZnO NRs p-n homojunction LEDs by using a simple p-type doping approach with Ag during the low-temperature solution process.