High bandwidth fluorescent color converters for white LEDs based visible light communications with various color...

Visible light communication (VLC) using white light-emitting diodes (LEDs) for simultaneous indoor illumination and high-speed wireless data transmission is a promising technology to complement radio in the upcoming wireless communication generations. However, commercially available white LEDs contain yellow phosphor coatings, which cause a significant limitation on the LED modulation bandwidth due to the long photoluminescence (PL) lifetime of phosphor materials. To overcome this bottleneck, it is essential to develop alternative color converters that are better suited for VLC applications. In this paper, we introduce a novel type of color converter made of a mixture of two organic fluorescent dyes: one with green emission and another with red emission. Our measurement results demonstrate that the fabricated converters simultaneously achieve high photoluminescence quantum yields (PLQYs) exceeding 60% and short PL lifetimes on the order of several nanoseconds. Furthermore, the combination of two dyes provides high flexibility in tuning the correlated color temperature (CCT) of the generated white light by adjusting the concentrations of the fluorescent dyes in the host materials, as well as the mixing ratio between these two dyes. As a result, both cool white and warm white light emissions were successfully generated. Our VLC transmission experiments show that the bandwidth of the white light generated by the use of the new color converters is no longer limited by their PL lifetime and therefore is significantly higher compared to that of a conventional phosphor-coated white LED. Moreover, the data transmission performances measured under various data rates and received signal strengths show that both the new cool white LED and the warm white LED have significantly lower bit error rates (BERs) compared to a conventional phosphor-coated white LED. Considering the forward error correction (FEC) limit of 3.8 × 10^-3, the new white LED transmitters achieve high transmission data rates that are approximately three times higher than those of a conventional phosphor-coated white LED.