Self-emitting yellow phosphor with enough quantum efficiency and thermal stability for light emitting diodes

Abstract

To get high quality white light from the combination of blue light emitting diode (LED) and yellow emitting YAG phosphor is still an issue. Herein, we report a self-emitting Zn₃(VO₄)₂ yellow phosphor synthesized by combustion method (CM) and co-precipitation method (CPM). Urea was used as a fuel for combustion and sodium hydroxide was used as precipitating agent for co-precipitation route. Under near UV excitation, the phosphors emit in the yellow region with an asymmetric emission band towards the higher wavelength in the range from 400 nm to over 800 nm due to the charge transfer transition of an electron from the oxygen to the tetrahedra VO₄ with T_d symmetry. The luminescence intensity for the CPM synthesized phosphor was much higher than the CM synthesized phosphor. Temperature dependent PL results suggested that the phosphor is thermally stable and retain its 80 % of the initial brightness at 353 K. The quantum efficiency of the CPM synthesized phosphor (∼ 33 %) is also most double the CM synthesized phosphor. The overall results suggest that a UV converted yellow emitting phosphor could be a potential alternative for the combination of blue and green phosphor used in WLED. As a result, the efficiency of the white LED can be enhanced by reducing the probability of the reabsorption.