Photoluminescence studies of ZnO thin films on R-plane sapphire substrates grown by sol-gel method

► ZnO thin films on R-plane sapphire substrates were grown by sol-gel method. ► Two emission peaks at 3.338 and 3.279 eV were observed at 300 K ► Activation energies of the two peaks were 39.3 and 28.9 meV,respectively. ► Exciton radiative lifetime of the two peaks increased with increasing temperature.