Influence of temperature and photoexcitation density on the quantum efficiency of defect emission in ZnO powders

The effect of laser excitation power density on the efficiency of intrinsic defect emission in ZnO powders was characterized by varying the laser irradiance over three orders of magnitude and monitoring changes in the samples' photoluminescence. The external quantum efficiency of the visible wavelength, broadband defect photoluminescence was found to depend not only on laser irradiance but also on temperature and prior annealing conditions. This material system is potentially useful as an ultraviolet-photoexcited, white light phosphor under low-power excitation (< 0.2 W/cm(2)) at room temperature and below. (c) 2007 American Institute of Physics.