Defect and energy transfer induced abnormal thermally stable and highly efficient narrow-band green emission

Efficient and thermally stable narrow-band green emitting phosphor is crucial for phosphor-converted light-emitting diodes (pc-LEDs), when they are used for backlighting device with wide color gamut. Herein, efficient narrow-band green-emitting Eu2+,Mn2+-activated Na/K-β-alumina phosphors are obtained, which exhibit anti-thermal quenching behavior (ATQ). The internal and external quantum efficiencies of optimal phosphor Na-β-alumina:0.2Eu2+,0.2Mn2+ are 81.8 and 55.4%, respectively, while those for K-β-alumina:0.2Eu2+,0.14Mn2+ are 90.7 and 67.8%, respectively, which are quite higher than those for Mn2+ singly doped one. The efficient energy transfer from Eu2+ to Mn2+ causes an efficient green emission with a peak at 510 nm and a FWHM value of 27 nm. Thermoluminescence indicates that the introduction of Eu2+ creates a trap energy level, which is responsible for the dramatic change from normal thermal quenching for Mn2+-activated β-alumina to anti-thermal quenching for Eu2+,Mn2+ co-activated ones. Furthermore, the ATQ effect gradually weakens and finally becomes zero thermal quenching within 150 °C in co-doped samples by increasing the Mn2+ content. By using the green-emitting component, the color gamut of the obtained pc-LED can reach 109% of the National Television System Council (NTSC) standard, which suggests its great application prospect for backlight.