Towards high performance cyan phosphor by replacing F− with Cl− in Ba3Ca2(PO4)3(F/Cl): Eu2+

Abstract

Currently, phosphor-converted white light-emitting diodes (pc-wLEDs) for solid-state lighting are mainly composed of blue or near-ultraviolet (n-UV) chips combined with phosphors. In the emission spectra of these pc-wLEDs, there always exists a missing valley in cyan region (from 470 to 510 nm). In order to achieve full-spectrum lighting, it is a challenging task to develop a cyan phosphor of high performance. In this work, a series of phosphors Ba2.97Ca2(PO4)3F1-xClx: 3%Eu2+ (x = 0-1) with apatite structure were synthesized and investigated. As Cl− replacing F−, the emission spectra of those phosphors present obvious blue-shift at 365 nm excitation. The obtained cyan phosphor Ba2.97Ca2(PO4)3Cl: 3%Eu2+ has higher quantum efficiency than the prototypical green phosphor Ba2.97Ca2(PO4)3F: 3%Eu2+ due to the smaller Stokes shift. As F− is replaced by Cl−, the band gap of the materials increases, which effectively reduces the probability of thermal ionization, thereby improving the thermal stability of luminescence (the integrated emission intensity of Ba2.97Ca2(PO4)3Cl: 3%Eu2+ at 150 °C can still maintain 81.2% of that at room temperature). The wLED fabricated has a high color rendering index and suitable correlated color temperature. This work develops a cyan phosphor with excellent performance, and it also can be as an important guidance for discovering novel excellent phosphors by the strategy of anionic substitution in the future.