Multistacked Detectors with Transparency-Controlled Polymer:Nonfullerene Bulk Heterojunction Sensing Layers for Visible Light Communications.

Here, we report multistacked organic photodiodes (OPDs) for potential light-fidelity (Li-Fi) detectors in visible light communications. The multistacked detectors were fabricated by integrating semitransparent inverted-type OPDs with polymer:nonfullerene bulk heterojunction (BHJ) layers. The thickness of BHJ sensing layers in the inverted-type OPDs was controlled to 30, 60, and 100 nm for top, middle, and bottom cells in the multistacked detectors, respectively, while 30 nm thick metal (silver) electrodes were used for securing both electrical conductivity and optical transparency. Results showed that each OPD cell in the multistacked detectors could deliver exact current signals upon illumination with a modulated white light from inorganic light-emitting diode lamp. The current signal from each OPD cell was linearly decreased as the modulation frequency of white light increased, supporting a stable operation of the multistacked detectors. Finally, the present multistacked detectors were able to exactly detect the programmed Li-Fi signals with a particular digitized information.