Synthesis and photoluminescence properties of a cyan-emitting phosphor Ca_3(PO_4)_2:Eu~(2+) for white light-emitting diodes

摘要

In this paper, a cyan-emitting phosphor Ca_3(PO_4)_2:Eu~(2+) (TCP:Eu~(2+)) was synthesized and evaluated as a candidate for white light emitting diodes (WLEDs). This phosphor shows strong and broad absorption in 250-450 nm region, but the emission spectrum is prominent at around 480 nm. The emission intensity of the TCP:Eu~(2+) was found to be 60% and 82% of that of the commercial BaMgAl_(10)O_(17):Eu~(2+) (BAM) under excitation at 340 nm and 370 nm, respectively. Upon excitation at 370 nm, the absolute internal and external quantum efficiencies of the Ca_3(PO_4)_2:1.5%Eu~(2+) are 60% and 42%, respectively. Moreover, a white LED lamp was fabricated by coating TCP:Eu~(2+) with a blue-emitting BAM and a red-emitting CaAlSiN_3:Eu~(2+) on a near-ultraviolet (375 nm) LED chip, driven by a 350 mA forward bias current, and it produces an intense white light with a color rendering index of 75.