White light emission from a blue LED, combined with a sodium salt of fluorescein dye

The bivalent sodium salt of fluorescein dye was successfully isolated. The maximum absorption and fluorescence emission wavelengths of the isolated fluorescein salt in epoxy were about 470 and 540 nm, respectively. The fluorescence quantum yield of the isolated salt in an epoxy matrix was measured to be 0.94. A hybrid light-emitting diode (LED) was fabricated using a blue light-emitting diode (LED, 460 nm) and the fluorescein salt dispersed in epoxy as the primary light source and luminescence converter, respectively. White light emission was observed when the salt concentration in the epoxy was 0.04 wt%. In the presence of DCM2 (a red dye, 8 wt% based on the salt), the CIE color coordinates of the hybrid LED system were closer to the pure white point. The conversion efficiencies of the system with and without DCM2 were 68 and 84%, respectively, which are higher than those reported so far in the literature.