Eu3+-Doped In2O3 Nanophosphors: Electronic Structure and Optical Characterization

Rare-earth ion-doped semiconducting nanocrystals have attracted extensive attention due to the ability to tailor their optical properties via size control and to achieve efficient luminescence through the host sensitization. A new type of nanophosphor based on Eu 3+ -ion-doped In 2 O 3 nanocrystals, synthesized via a facile solvothermal method, shows intense and well-resolved intra4f emissions of Eu 3+ upon bandgap excitation. Optical properties of Eu 3+ occupying two crystallographic sites (C 2 and S 6 ) are systematically investigated by means of high-resolution emission and excitation spectra at 10−300 K. The crystal-field (CF) analysis and Judd−Ofelt (JO) intensity calculation of Eu 3+ at C 2 site yield relatively large CF strength and JO intensity parameters, indicating the good optical performance of this nanophosphor. Due to a small filling factor (0.43) of the In 2 O 3 nanocrystals, the radiative lifetime of 5 D 0 of Eu 3+ is found to be significantly affected by the surrounding media with various refractive indices, which is about 3 times longer than that in the submicrometer counterparts. Furthermore, as compared to the submicrometer counterparts, an enhanced host-to-Eu 3+ energy transfer with higher quenching temperature is observed due to more effective photon-induced carrier localization and trapping around Eu 3+ in nanocrystals.