Abstract:
A vacancy-activated intrinsic white light emitting phosphor - a new stoichiometric single-phase Ba3V4O13, has been synthesized by rapid and efficient microwave synthesis in 15 min at 200 degrees C. The phosphor exhibits long-range disorder and morphology transformation from rod to sheet-like in 30 min and to spherical shape (similar to 50 +/- 5 nm) upon raising the temperature to 220 degrees C, owing to dissolution and subsequent recrystallization. There is the appearance of a V4+ state, formed by the reduction of V5+, implying the creation of oxygen vacancies (VO). The detailed first-principal calculations and experimental data reveal rearrangement in the band structure following the generation of VO, resulting in the narrowing of the EVB maxima and ECB minima. The optimized BVO-200-15 exhibits white light emission with CIE (0.333, 0.368) and 23.3% internal quantum efficiency, resulting from charge transfer-based blue-green emission within the tetrahedral VO43- moiety, along with VO related red emission, and is stable up to 250 degrees C. The mechanistic investigations reveal two radiative states at low temperatures (90-270 K), and three radiative states at room temperature further confirmed by time resolved emission spectra (TRES). By employing a down-conversion BVO-200-15 phosphor, a stable single-phosphor-based white light-emitting prototype was fabricated, exhibiting a high color rendering index (CRI) of 86.1, correlated color temperature (CCT) of 5998 K, and high luminous efficacy (LE) of similar to 128.4 lm W-1. Schematic showing the synthesis of a new stoichiometric single-phase Ba3V4O13, its vacancy-activated intrinsic white light emission, and the W-LED prototype with CCT similar to 5998 K, high CRI similar to 86.1, and LE of similar to 128.4 lm W-1.