Organic semiconductors offer many potential advantages as a novel color converter for VLC due to their visible band gaps, short radiative lifetime, and high photoluminescence quantum yield (PLQY). This combination of properties implies that the key figure of merit for color converter materials is a short natural radiative lifetime. 5, 6 There is currently a strong need for alternative materials for fast color converters, which can combine high illumination performance with short PL lifetimes.
2 The photoluminescence (PL) lifetime typical of the phosphor materials used is on the microsecond timescale, which limits the system bandwidth to a few megahertz (MHz). 4 PcLEDs can operate at high efficiency and brightness, but the long excited state lifetime of the phosphors restricts modulation frequency and hence the transmission rate. In addition, it must emit sufficient optical power to create the required signal-to-noise ratio at the receiver for the particular modulation format used.Ĭonventional phosphor-converted LEDs (pcLEDs) use a blue InGaN LED coated with a yellow phosphor to convert a fraction of the blue light to longer wavelengths. 1- 3 Data are encoded by modulating the light source, and the rate of data transmission that can be achieved depends on the modulation bandwidth of the LED and its phosphor coating. The adoption of light-emitting diode (LED) lighting makes this possible, as standard lighting fixtures can be used for both illumination and data communications. Visible light communications (VLC) offers a means to do this, using the unlicensed visible region of the electromagnetic spectrum for wireless communications, where hundreds of terahertz of bandwidth are available. The ever growing demand for wireless data communications is driving a need for new technologies to augment the existing radio frequency approaches (such as WiFi). This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
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