Thermal stabilities of cadmium selenide and cadmium-free quantum dots in quantum dot-silicone nanocomposites

To investigate the thermal stabilities of CdSe and Cd-free quantum dots (QDs) in QD-silicone polymer nanocomposites, we synthesized both CdSe and CuInS2 (CIS) QDs capped with different surface ligands (oleic acid (OA) and 1-dodecanethiol (1-DDT)). A comparison of the quantum yields of dried QDs after exposure to different temperatures revealed that the CIS QDs and 1-DDT ligands exhibited higher thermal stabilities than the CdSe QDs and OA ligands, respectively. We also prepared QD-silicone nanocomposites containing different types of QDs by varying the curing temperature and time and observed that nanocomposites containing CdSe QDs exhibited discoloration at high temperatures, whereas those containing CIS QDs did not. Moreover, the highest quantum efficiency (QE) of the QD-silicone nanocomposites was observed in the case of CIS QDs capped with 1-DDT and the lowest was observed in the case of CdSe QDs capped with OA. Because the dispersion states of QDs were not substantially affected at high temperatures, we attributed the high QE of nanocomposites containing the CIS QDs capped with 1-DDT to the superior thermal stability of CIS QDs and their surface ligand (i.e., 1-DDT).