Exciton-Phonon Interaction and Role of defect/trap states in CdSe Quantum Dots

Abstract Semiconductor quantum dots have become potential candidate for application in LEDs, diode lasers, solar cells and biological labelling. Basic understanding of their photo physical processes affecting their optical transition characteristics is required for their efficient use in different applications. We report here role of phonons and defect/trap states on the photoluminescence intensity inferred from temperature dependence of integrated intensity of main excitonic peak in the temperature range 30-300 K. Clear demarcation of two photoluminescence quenching processes operative in low and high temperature regions has been observed. We find the thermal activation energy of the trap states to be ∼ 7 meV for main excitonic emission peak and ∼ 10.5 meV for deep trap emission. Thermal escape is assisted by three phonons inferred from both emission peak analysis.