Hybrid YAG/CdSe Quantum Dots Phosphors for White Light-Emitting Diodes

CdSe quantum dots (QDs) with the emission wavelength of 577 nm, full width at half maximum (FWHM) of 28 nm, quantum yield (QY) of 40% and average particle size of 3.7 +/- 0.5 nm are prepared. 1, 3 and 5 wt% of CdSe QDs is blended with commercial YAG:Ce phosphor (called as composite phosphor) and the device performance of YAG-based and composite phosphor-based white light-emitting diode (WLED) is investigated. The color rendering index (CRI) and luminous efficiency could be improved simultaneous for composite phosphor-based WLED. As the applied current increases, the correlated color temperature (CCT), Commission International d'Eclairage (CIE) chromaticity coordinates and CRI of both WLEDs are almost the same when compared with standard condition (20 mA), while the luminous efficiency of both WLEDs decreases with increasing applied current. It is interesting to find that there is a positive effect of QDs on the luminous efficiency and CRI value. This result also reveals that adding a small amount of yellow emitting QDs can not only reduce the scattering-of light effectively but increase utilization efficiency of reflection and refraction light, thereby enhancing the efficiency of composite phosphor-based WLED. Moreover, the emission wavelength of 577 nm QDs is longer than that of YAG, it redound to extends emission range resulting in increase the CRI of devices.