Photoluminescence enhancement from the defects state formed by neutron/gamma mixed irradiation in an epoxy resin for LED applications

In the framework of the ICERR (International CEntres based on Research Reactors) project, the effect of neutron/gamma irradiation on material has been studied. In this work, we investigate the mixed neutron/gamma irradiation effects on the optical properties of epoxy resin polymers. Photoluminescence (PL) measurements are used in epoxy resin films irradiated in the dose range from 0 to 900Gy. For more information about the carriers dynamics, we studied their activation energy and phononic processes through the analysis of the PL spectrum evolution as a function of temperature. Mostly, materials irradiation studies by ionizing sources show a generation of defects and subsequently lead to the damage and degradation on the different properties. In this study we have shown an advantage of neutron/gamma irradiation, it is the improvement of the luminescence properties. The 500Gy dose has the highest quantum yield at low temperature. But the 600Gy dose shows the highest yield at room temperature. For the 500Gy dose, the neutron/gamma treatment mainly favored the activation of carriers from lower to higher levels. On the other side with the 600Gy dose, there was a combination between the activation of carriers from lower to higher levels and the ionization of trapped electrons in the defects centers.