Temperature-dependent photoluminescence study of InP/ZnS quantum dots

This paper reports on the temperature-dependent photoluminescence of InP/ZnS quantum dots under 532 nm excitation, which is above the InP transition energy but well below that of ZnS. The overall photoluminescence spectra show two spectral components. The higher-energy one (named X) is assigned to originate from the excitonic transition; while the low-energy spectral component (named I) is normally interpreted as resulting from lattice imperfections in the crystalline structure of InP/ZnS quantum dots (QDs). Peak positions of both the X and I emissions vary similarly with increasing temperature and the same as the InP bandgap narrowing with temperature. In the temperature range from 15 to 80K, the ratio of the integrated intensity from the X and the I emissions decreases gradually and then this ratio increases fast at temperatures higher than 80K. This could result from a population of charge carriers in the lattice imperfection states at a temperature below 80K to increase the I emission but then with these charge carriers being released to contribute to the X emission.