Low-Concentration Eu2+-Doped SrAlSi4N7: Ce3+ Yellow Phosphor for wLEDs with Improved Color-Rendering Index

摘要

Luminescence property of low-concentration Eu2+-doped SrAlSi4N7:Ce3+ yellow phosphor is reported in this paper. Three optical centers Ce1, Ce2, and Eu2 are observed in the phosphor. Deconvolution of emission spectrum confirms the three centers to be green (530 nm), yellow (580 nm), and red (630 nm), respectively. This property promises considerable improvement of color-rendering property of a white light-emitting diode (wLED). For example, color-rendering index (CRI) of wLED fabricated by combining a blue LED chip and SrAlSi4N7:0.05Ce(3+),0.01Eu(2+) phosphor reaches 88. A competitive energy transfer process between Ce1Ce2 and Ce1Eu2 is confirmed based on InokutiHirayama formula. Ratio of energy transfer rate between Ce1Ce2 and Ce1Eu2 (WEu2/W-Ce1Ce2) is calculated to be 2.0. This result reveals the effect of Eu2+ concentration on quantity of green and red components in SrAlSi4N7:Ce3+,Eu2+ phosphor.