Anti-thermal-quenching, color-tunable and ultra-narrow-band cyan green-emitting phosphor for w-LEDs with enhanced color rendering

Abstract

Highly efficient cyan/green phosphors are identified as functional block to fulfill the cyan gap in emissive spectra of traditional white light emitting diodes (w-LEDs). Herein, a series of emission-tunable solid solution phosphors, namely KAl11-xGaxO17:Mn2+ (x = 0–11), with superior luminescence properties and anti-thermal-quenching behavior is reported. KAl11O17:Mn2+ dedicates green emission at 510 nm with a narrow full width at half maximum of 23.5 nm, and excellent thermal quenching resistance (130.4% at 150 °C) due to the thermal induced electron detrapping. Interestingly, doping Ga3+ ions into this hexaaluminate matrix enables harvested phosphor with enhanced emission by 2.35 times, and achieves luminescence tuning from green to cyan. Moreover, such a Ga3+ substituting could stabilize the luminescence (nearly zero-thermal-quenching) of phosphor even at the elevated temperature range of 25–250 °C. Based on the thermoluminescence (TL) analysis and density functional theory (DFT) calculations, this extraordinary phenomenon was reasonably assigned to the enhancement of photoionization effect and the detrapping of the captured electrons from shallow trap state. The w-LEDs fabricated by employing KAl11-xGaxO17:Mn2+ as cyan/green emitting component show superior color rendering index (improved from 85.5 to 96.3), indicating these Mn2+-doped hexaaluminate phosphors may be candidates used for high-power w-LEDs in the future. This work opens up a new pathway to construct anti-thermal-quenching and spectra-tunable phosphors for optical applications.