Poor near-band-edge emission (NBE) prohibits the application of solution-grown ZnO nanorods in optoelectronics, thus their photoluminescence (PL) was studied with respect to post-annealing temperature and duration. A universal behavior was revealed: NBE was enhanced by one order (or two) of magnitude after annealing in air (or H2) at about 425 °C for 30 min, while the enhancement factor starts to decrease after annealing at higher temperatures. The evolution of PL was mainly ascribed to annealing-induced activation and dissociation of hydrogen donor, which was identified as HO by both PL and Raman analyses. Results from nanorods with different diameters and annealing gases further support this assignment. The results provide new insights to understand and optimize the properties of solution-grown ZnO.
