A thermally stable warm WLED obtained by screen-printing a red phosphor layer on the LuAG:Ce3+ PiG substrate

Abstract

Currently, phosphor-in-glass (PiG) approach draws great attention because of its excellent thermal resistance and facile process in WLED fabrication. However, the red light deficiency results in high correlated color temperature (CCT) and low color rendering index (CRI) in white light-emitting diode (WLED). Herein, a new LuAG:Ce3+ phosphor-in-glass (Lu-PiG) combining with the CaAlSiN3:Eu2+ red phosphor layer was synthesized by the low temperature co-sintering and screen-printing techniques, which was experimentally demonstrated to replace the conventional polymer-based phosphor converter and realized the chromaticity tuning for LuAG:Ce3+ phosphor with WLED. The Lu-PiG constructed WLED exhibited excellent thermal stability, but it still showed a typical cold white light resulting from the absence of red light component. Therefore, a stacking geometric configuration by screen-printing a red phosphor layer on the Lu-PiG substrate (R&Lu-PiG) was designed to solve red deficiency problem. The R&Lu-PiG color converter showed an excellent thermal stability with only 8.2% emission loss compared to the Lu-PiG when elevating temperature from 303K to 433K. By adjusting the CaAlSiN3:Eu2+ phosphor content in the layer, we obtained a high-performance warm WLED with a luminous efficacy of 102.1lm/W, a CCT of 3410K and a CRI of 76.5 under 20mA current driving. Thus, it is expected that this developed R&Lu-PiG color converters could have large potential applications in high-power warm WLED.