A light-emitting and detecting bifunctional device based on the bias-selective redox activity of a polymer

Abstract

We propose an approach featuring a bifunctional organic device designed to serve as both a light-emitting electrochemical cell and a photodetector in a unified platform. This device enables controlled light emission and detection by manipulating the bias direction and magnitude, leveraging the selective redox activity induced by the ionic liquid. The two-terminal device operates through two key mechanisms: Under reverse bias, the anions, serving as a p-type dopant, permeate the active layer (P3HT), augmenting the photoconductive gain. Conversely, forward bias causes cations to penetrate the P3HT, inducing an n-doping effect, creating a p–i–n junction similar to light-emitting electrochemical cells (LECs). This bias-dependent redox activity combines the features of a photodetector with exceptional performance: an EQE of 10 000%, alongside LEC with a luminance of 17 cd m⁻². The successful creation of a two-way VLC system using reverse- or forward-biased devices demonstrated consistent data transmission and reception.