As a first part of this presentation, a multichannel/multicolor visible light communication (VLC) system using entirely organic components, including organic light emitting diodes (OLEDs) and organic photodiodes (OPDs), is developed to demonstrate indoor lighting applications where the integration of OLEDs and OPDs has significant potential. To achieve this, tricolor (R/G/B)-selective OPD arrays for the receiver and tricolor OLED arrays for the emitter are developed. For (R/G/B)-selective OPDs, a Fabry-Pérot electrode structure to enhance color selectivity and a thick junction structure to effectively accommodate a wide range of driving voltages are introduced. For tricolor OLEDs, fluorescent-emitting materials are used to enhance the operating frequency in addition to introducing a cavity structure to achieve narrow emission. Utilizing these spectrally refined tricolor OPDs/OLEDs, a VLC system is designed for indoor lighting applications, and a systematic analysis of their signal-to-interference ratio dependence on the distance or angle between the transmitter and receiver is performed. The study’s findings indicate the importance of emission angle-dependent wavelength shift of the OLED and the luminosity function, which varies with wavelength, in the R/G/B mixed-white-light-based VLC systems. Finally, the feasibility of VLC using tricolor OPDs/OLEDs in the real-life context of indoor white-color lighting is demonstrated, showing that the transmitted data patterns well-matched the received data patterns.

 As a second part, I will introduce a mutual VLC system using light emitting/light detecting bifunctional organic devices. A new, dual-function organic diode capable of both light emission and detection, based on a streamlined ITO/PEDOT:PSS/P3HT/P(VDF-TrFE)/Al device architecture is introduced. This device architecture is synergistically coupled with an ionic liquid ([EMIM]⁺[OTf]^-) to enable bias-selective redox activity, achieved by treating the PEDOT:PSS solution with an ionic liquid. Under reverse bias, anionic [OTf]- species infiltrate the P3HT active layer, creating a high permittivity depletion region. In this region, photogenerated charges are confined at the P3HT/P(VDF-TrFE) interface, enabling trap-assisted photomultiplication OPD. Conversely, a forward bias injects cations ([EMIM]⁺) into the P3HT layer, inducing n-type doping in proximity near the P3HT/P(VDF-TrFE) interface, thereby engendering a PIN junction analogous to light-emitting electrochemical cells. This fruitful approach yields a successful dual-function diode, showcasing distinctive traits of an OPD and an OLED, highlighting its dual-functionality. Finally, the feasibility of mutual VLC using OPD/OLED dual-function diode is demonstrated.