Enhanced quantum efficiency and thermal stability of cyan-green emitting BaLu2Al3ScGeO12: Ce3+, Si4+ phosphor via cation substitution for WLEDs

The advancement in the development of high-efficiency cyan-green emitting phosphors is pivotal for achieving high-color-quality full-visible-spectrum white light-emitting diodes (WLEDs). In this study, a series of novel cyan-green emitting BaLu 2 Al 3 ScGe 1- y Si y O 12 : x Ce 3+ (BLASGe 1- y Si y O: x Ce 3+ ) phosphors were successfully synthesized. X-ray diffraction analysis confirmed that all samples possess a typical garnet crystal structure, belonging to the Ia 3 ̅ d space group. The emission spectra of these BLASGe 1- y Si y O: x Ce 3+ phosphors effectively bridge the “cyan gap” within the 480–520 nm cyan-green emission region. Under 438 nm blue light excitation, the prepared BLASGO: Ce 3+ phosphor exhibits broad-band cyan-green emission with an emission peak at 504 nm and a full width at half maximum (FWHM) of 103 nm, thereby significantly enhancing cyan emission while preserving green emission. More importantly, by substituting Ge 4+ ions with smaller Si 4+ ions, the internal quantum efficiency (IQE) and thermal stability of the phosphor are markedly improved due to the highly symmetrical rigid structure. The optimized BLASSO: Ce 3+ phosphor demonstrates superior cyan-green emission performance with a high internal quantum efficiency of 93.28 % (an enhancement of 31.23 %) and thermal stability increased to 69.62 %. Based on the developed BLASSO: Ce 3+ cyan-green phosphor, a high-performance full-visible-spectrum WLED device was successfully fabricated, featuring a high color rendering index (CRI or R a , R a = 93.4) and a low correlated color temperature (CCT = 2814 K).