Triple-layer remote phosphor: An improved structure with higher color quality and luminous flux of white LEDs

Abstract

This research suggests using triple-layer remote phosphor (TRP) to improve the color quality and luminous flux coming out of white LEDs (WLEDs). The TRP structure contains three different phosphor layers: beneath is the yellow phosphor YAG:Ce3+, a red phosphor LiInO2:Eu3+ above, and a green phosphor Zn2GeO4:Mn2+ in within. Controlling the red-light composition with a red phosphor layer LiInO2:Eu3+ leads to a higher color rendering index (CRI). Thus, increase the luminous efficacy (LE) of WLEDs using a green phosphor layer of CaLaB3O7:Ce3+,Mn2+ to monitor green light composition. Additionally, when increasing these two phosphor concentrations, the yellow concentration YAG:Ce3+ decreases to keep the average correlated color temperatures (ACCTs) within 6000K - 8500K. Besides CRI and LE, controlling green and red phosphor concentration is also a way to analyze the color quality scale (CQS). The study result shows that the higher the LiInO2:Eu3+ concentration, the greater the CRI value. However, CRI significantly reduces when increasing Zn2GeO4:Mn2+ concentration. Meanwhile, CQS can raise a substantial amount in the concentration range of 10%-14% LiInO2:Eu3+, flout LiInO2:Eu3+ concentration. Peculiarly, parallel with the improvement of CRI and CQS, LE also grows over 40% due to a decrease in backscattering light and added green light. This research may be valuable for manufactures for improving the color quality and luminous flux of WLEDs.