When visible light communications meet photonic nanostructures

Organic light-emitting semiconductors present much shorter lifetimes compared to conventional phosphor colour converters, therefore capable of achieving much higher bandwidths in visible light communications. This talk focuses on addressing two of the coming challenges for organic semiconductors: spatial multiplexing and bandwidth enhancement, and explores the roles of photonic nanostructures as a solution to both challenges. The appealing features of visible light communications (VLC), including fast speed, numerous unregulated bandwidth and high security, make VLC an important and promising supplement to the existing Wi-Fi network for the coming 5G communications [1-4]. So far most of the fast VLC links are based on micro-LEDs or laser diodes (LD) which have bandwidths at GHz level, however, in order to achieve high-quality white light, a practical and simple way is to combine a colour converter with the fast-modulated blue LED/LD backlight. Conventional phosphors have bandwidths of only several MHz, so the overall bandwidths of white light sources are severely limited. Organic light-emitting semiconductors have demonstrated intriguing capabilities of boosting bandwidths due to their nanosecond-scale lifetimes [5-10]. For example, conjugated polymers demonstrate bandwidths of over 200 MHz, which are enhanced by two orders of magnitude compared to those of conventional phosphors. This talk focuses on addressing two of the coming challenges for organic semiconductors: i) Can organic semiconductors be applied for parallel communications like multiple-in-multiple-out (MIMO)? ii) Are there potential solutions to further improve the bandwidths of organic semiconductors if the molecular design of fast organic emitters has reached its bottleneck? Colour tuning for organic semiconductors is facile, so parallel communications based on wavelength division multiplexing can be easily realised. On the contrary, organic semiconductors are not born for spatial multiplexing, since they are generally Lambertian emitters. Our strategy to overcome this problem is to use photonic.