High-Performance Rare-Earth-Free Fluorophores: toward White LEDs

A series of down-converting organic fluorophores were synthesized in order to cover the full range of the visible spectrum, two pi-extended phospholes with blue (B) and red (R) emissions, and two difluoroboron beta-diketonates with green (G) and yellow (Y) emissions. Their excellent optical performances were evidenced by recording their emission spectra and measuring their photoluminescent absolute quantum yields in both the liquid and solid states. Subsequently, these fluorophores were incorporated into silicone at 10 wt % to prepare luminescent composite films. Their photoluminescent properties were analyzed at room temperature, and their CIE chromaticity coordinates were determined. By strategically combining these films emitting different visible lights (B, G, Y, R) with commercial blue or violet light-emitting diode (LED) chips, we were able to produce white light exhibiting a high color rendering index (90) and color correlated temperature close to 4500 K. Finally, to assess the durability of these composite films and to demonstrate the potential of these rare-earth-free fluorophores as down-converters phosphors for LED-based devices, the stability of their optical performances was investigated upon thermal and photonic stresses.