High-excitation effect on photoluminescence of sol-gel ZnO nanopowder

We studied the power-dependent photoluminescence of ZnO nanopowder grown by sol-gel method at low temperature. At moderate optical pumping intensity, two nonlinear emission bands due to the radiative recombination of free biexciton and the inelastic exciton-exciton scattering were detected. We found that the threshold of the excitation density for the emergence of the nonlinear emission bands is low (< 18 W/cm(2)) in sol-gel ZnO nanopowders.