UV-excited single-component white phosphor of Lu2WO6 with broad-band emission for pc-WLED

Abstract

Obtaining white light from a single-component phosphor is still a significant challenge due to the complex energy transfer between multiple luminescent centers. Herein, white light emission is obtained in a single-component lutetium tungstate without any doping elements. By tuning the pH values during the hydrothermal synthesis, the orthorhombic Lu₂W₃O₁₂ transformed into monocline Lu₆WO₁₂ and rhombohedra Lu₆WO₁₂. Only the monoclinic Lu₂WO₆ phase emitted light, whereas the other two phases did not. The main reason was that the exciton binding energy of Lu₂WO₆ was larger than that of Lu₂W₃O₁₂ and Lu₆WO₁₂. Except for the 480 nm intrinsic emission of Lu₂WO₆, new long-wavelength excitation and emission bands were observed with the center at 340 nm and 520 nm. Based on the first-principle calculation, this new photoluminescence band comes from the electron transition between the local states of oxygen vacancies and valence band. Owing to this new broad-band emission, the white light LED lamp is fabricated by combining Lu₂WO₆ phosphor synthesized at pH values of 4.5 and 6 and 365 nm LED chips. The CIE coordinates of the pc-WLEDs are (0.346, 0.359) and (0.380, 0.380), respectively, and both are located in the white light region. Our research demonstrated a facile way to obtain a single-component white light emission phosphor without any doping components for pc-WLED applications.