"Visible Light Communication (VLC)" is the best candidate for the next generation of network communication owing to its wide bandwidths and compatibility with solid-state lighting devices. As shown in Figure 1, our research features a new type of multilevel photosensing memory based on a thin film transistor, where the zinc tin oxide (ZTO) is added with gold nanoparticles to form a "co-active layer" in order to expand the visible light sensing spectrum and efficiently convert the light signal into a current signal. The interface between the gold nanoparticle and the oxide semiconductor has the ability to capture or release electrons, which can further control the intensity of the current signal, thereby completely storing the optical data represented by the current signal. In addition, this device can respond to light signals of different wavelengths or intensities, and further exhibits the multilevel photosensing memory, as depicted in Figure 2. As a result, it is possible to integrate the photosensing, computing and memory components for VLC into one. It not only simplifies the production process and reduces the cost, but also accelerates the signal transmission, which further advances the future mobile communication devices.

Figure 1. Schematic illustration of the multilevel photosensing memory

Figure 2. The retention of the multilevel photosensing memory after 405, 520, 635 nm light illumination