Unravelling the white light emission in a single-phase new stoichiometric vanadate phosphor synthesized by rapid low-temperature one-pot synthesis and its W-LED prototype with high CRI and luminous efficacy

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 °C. The phosphor exhibits long-range disorder and morphology transformation from rod to sheet-like in 30 min and to spherical shape (∼50 ± 5 nm) upon raising the temperature to 220 °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 (V_O). The detailed first-principal calculations and experimental data reveal rearrangement in the band structure following the generation of V_O, resulting in the narrowing of the E_VB maxima and E_CB 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 V_O related red emission, and is stable up to 250 °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 ∼128.4 lm W⁻¹.