Correlation of quantum efficiency and photoluminescence lifetime of ZnO tetrapods grown at different temperatures

Abstract

Absolute external quantum efficiencies (ηs) and photoluminescence (PL) decay lifetimes of ZnO tetrapods grown at different temperatures were measured. All the tetrapods had an UV peak at about 390 nm and a very weak defect emission. Measurements showed that the tetrapods have ηs of 2%-4% at room temperature. The sample, grown at optimal temperature, exhibited the largest absolute η of 4.3% and longest PL decay lifetimes among all the samples. These results showed that precise control of growth temperature plays an important role in making high quality ZnO tetrapods. In time-resolved measurement, the PL decay time constant (τ) versus temperature is well fitted by the theoretical prediction τ = a . This increase in PL lifetime with increasing temperature shows that the excited state relaxation is dominated by radiative recombination.