Crystallographic site engineering of single Bi3+-doped single-component Ca5Ga6O14:Bi3+ phosphor for full-spectrum white light emission and highly sensitive optical thermometer

Abstract

The development of single-activator-doped, single-component full-spectrum white light emission materials is essential for human-centric lighting. Here, full-spectrum white-light emission (350-800 nm) was achieved in a single-Bi3+ -doped single-component phosphor Ca5Ga6O14:xBi3+ via crystallographic site engineering. The ultra-broadband emission comprises three distinct emission bands centred at 374, 515 and 620 nm, arising from Bi 3+ activators occupying Ca3, Ca2, and Ca1 sites in Ca5Ga6O14:xBi3+, respectively. These spectral components produce high-quality white light with a superior colour rendering index of 91.0 and a correlated colour temperature of 4820 K for the prototype pc-WLED devices fabricated by coating the optimised phosphors onto a UV LED chip. Notably, the 347 and 515 nm emissions exhibit typical thermal quenching (TQ) upon heating, whereas the 620 nm emission shows an unusual excitation wavelength-dependent transition from anti-TQ to normal TQ due to preferential energy compensation from the defect energy levels. This unique thermal response endows Ca5Ga6O14:xBi3+ with an outstanding maximum relative sensitivity of 5.12% K-1 in fluorescence intensity ratio (FIR)-based thermometry, outperforming hitherto reported single Bi3+-doped ratiometric thermometers. The rational design of Ca5Ga6O14:xBi3+ marks a significant advance toward single-component, multi-functional phosphors capable of simultaneous full-spectrum white light generation and temperature sensing, highlighting crystallographic site engineering as a powerful strategy for smart luminescent materials in advanced lighting and sensing applications.