A comparative study of organic photodetectors based on P3HT and PTB7 polymers for visible light communication

Visible light communication (VLC) is a promising candidate to face the bandwidth limitation problems of traditional radio communication system. The use of a light emitting diode (LED), directly modulated, as a transmitter of the wireless telecommunication link permits the installation of VLC-based systems in practically all human-attended settings (home, office, markets). However, a drawback of VLC systems remains the receiver side, due to the lack of photovoltaic devices for this specific application. Organic electronics based on solution processed technologies has the great potential to be applied in VLC systems, building effective, scalable and low-cost photodetectors. We have investigated the effect of the device architecture on optical and electrical device performance, using both P3HT:PCBM and PTB7:PC70BM bulk-heterojunction active layers. We have established that both materials and structures could affect greatly the device properties, and we have provided an analytical representation of the spectral matching between light source and detector. In particular, the most promising device, based on a P3HT:PCBM blend, has demonstrated high performance, especially using an inverted structure. In this configuration, a device cut-off frequency of ~1.0 MHz has been achieved, paying the way to organic photodetector application on VLC-based telecommunication systems in 5G scenarios.