Proton irradiation effect on cadmium selenide-zinc sulfide core-shell nanocrystals embedded in ultraviolet curable resin

The effect of proton irradiation on the optical properties of CdSe-ZnS core-shell nanocrystals embedded in ultra-violet curable resin has been investigated using optical absorbance and photoluminescence (PL) techniques. Nanocrystals (NCs) of three different diameters, 4.5nm, 2.7nm and 2.1nm were used for the experiments and they showed the first exciton transition at wavelengths 600nm, 552nm and 498nm respectively. These NCs were subjected to 2MeV protons at different fluences ranging from 5 x 1013 protons-cm -2 to 9.5 x 1015 protons-cm-2. The integrated area of excitonic transition observed from absorbance spectra was monitored as a function of proton fluence. The results indicate that there was little effect of the proton irradiation doses up to 9.03 x 1015 protons-cm -2 on the excitonic transitions in 4.5nm NCs. However there was some radiation-related degradation observed in lower size NCs. No excitonic transition was observed in 2.1nm NCs from the fluence of 6 x 1015 protons-cm -2. This can be attributed to the probable degradation in the UV curable resin with the increasing proton fluence. Further photoluminescence (PL) measurements conducted on 4.5nm NCs have shown degradation in the PL intensity with the increasing proton fluences when measured at 300K and 77K. The degradation of resin appears to be the limiting factor in determining the maximum tolerable fluence level of NCs. However, it can be stated that CdSe-ZnS core-shell nanocrystals are much more radiation tolerant than many materials used in space solar applications.