Blue-light excitable La2Ce2O7:Eu3+ red phosphors for white light-emitting diodes

Abstract

Inorganic phosphors which can be effectively excited with blue-light are highly desirable for white light-emitting diodes (WLEDs). Herein, Eu3+-activated La2Ce2O7 phosphors are prepared by a self-rising reaction using urea and glycine as leavening agents under hydrothermal conditions. The phosphors display a well-distributed round or elliptical particle shapes with an average diameter of about 55 ± 10 nm. The excitation spectrum is dominated by the 7F0→5D2 transition (∼465 nm) that overlaps the emission of efficient blue emitting LEDs, rendering these phosphors as very attractive as blue down converters. The luminescence performance can be effectively improved by optimizing the molar ratios of leavening agents and the content of Eu3+ concentration and, thus, the absolute quantum yield can reach 0.229 ± 0.023. By combining a commercial blue emitting LED chip (InGaN, 465 nm) and the phosphors, intriguing efficient pure red emission is achieved with International Commission on Illumination (CIE) color coordinates of (0.669,0.330). This pure red emission is used to tune the well-known poor correlated color temperature values of WLEDs based on YAG:Ce3+. WLEDs are fabricated by coating LED chips emitting in the blue with blends of YAG:Ce3+ and Eu3+-activated La2Ce2O7, yielding prototypes with enhanced color rendering index that is easily adjusted from 7119 to 3242 K, demonstrating that this strategy may use to complement the red component in WLEDs.