Enhanced Ce3+ photoluminescence by Li+ co-doping in CaO phosphor and its use in blue-pumped white LEDs

In this paper, we demonstrate a method to improve the photoluminescence of CaO: Ce3+ phosphor and delineate its first use in blue-pumped white LEDs. The results show that the yellow emission of Ce3+ is enhanced by a factor of 1.88 by adding Li+ into CaO host at 474 nm blue light excitation. On analyzing the diffuse reflection spectra and fluorescence decay curves, we reveal that the photoluminescence enhancement is originated from the rise of absorbance to the excitation photons but not from the improvement of the luminescent efficiency. Li+-improved CaO: Ce3+ exhibits more red component when it is compared with the commercial Y3Al5O12: Ce3+ (YAG: Ce3+) phosphor, indicating its potential application for high color rendering white LEDs. Thus, a white LED is fabricated by combining blue InGaN LED chip with CaO: Ce3+, Li+ phosphor and a warm white light with high color rendering index (Ra) of 80, low correlated color temperature (Tc) of 4524 K, and sufficient luminous efficiency of 50 lm W−1 is obtained.