Electronic structure and luminescence properties of Tb3+ -activated NaBaBO3 green-emitting phosphor

A novel green-emitting phosphor Tb3+ doped NaBaBO3 was prepared using a conventional high temperature solid-state reaction method. The crystal structure and luminescence properties of NaBaBO3:Tb3+ were studied. The NaBaBO3 host was also investigated using density functional theory calculations. Our calculated lattice parameters of NaBaBO3 host were found to be in excellent agreement with experiment. Theoretically, the host matrix NaBaBO3 was a wide-gap semiconductor with a direct band gap of 3.66 eV, where the bottom of conduction band and the top of valence band were dominated by Ba 5d state and O 2p state, respectively. The excitation spectra indicated that the phosphor could be effectively excited by near ultraviolet light. The phosphor featured a satisfactory green performance with the highest photoluminescence intensity located at 543 nm excited by 377 nm light and the measured Commission Internationale de L'Eclairage (CIE) chromaticity was determined to be (0.2860, 0.4640). The optimum Tb3+ concentration in NaBaBO3 was 5.0 mol.%. The concentration quenching occurred when Tb3+ concentration was beyond 5.0 mol.% and the concentration quenching mechanism could be explained by the dipole-dipole interaction. The effects of charge compensators (including Li+, Na+ and K+) and temperature on the photoluminescence of NaBaBO3:Tb3+ were also studied. The present work suggested that the NaBaBO3:Tb3+ phosphor was a promising green-emitting material for near ultraviolet white light-emitting diodes.