Nano-silver/MoS₂/nano-silver bipolar photodetector and its symmetric ternary-encoded image transmission

Bipolar photodetectors, characterized by their dual positive/negative response, hold significant promise for applications in image encoding and optical communication. This study proposes a bipolar-responsive nano-silver/MoS₂/nano-silver optoelectronic device with an asymmetric Schottky junction. The asymmetry is precisely controlled through the dimensions and thickness of the electrodes to generate a significant work function difference. This design enabled optical modulation of the metal-semiconductor contact potential, allowing reversible polarity switching through photogenerated potential-driven electric field reorientation. When incident light with a wavelength of 650 nm illuminated various positions on the device, three distinct logical states (-1, 0, +1) were observed. This unique capability was applied to symmetric ternary encoding and transmission of grayscale images, reducing data volume by 75% compared to traditional binary encoding. Quantitative evaluation of reconstructed images demonstrated acceptable quality with a peak signal-to-noise ratio (PSNR) of 29.04 dB and structural similarity index (SSIM) of 0.9060. Notably, all critical characteristic information remains preserved, despite the introduction of minor noise during the encoding process. This work presents an asymmetric dual-aurora electrical detector with potential for efficient image-encoded transmission and high-density communication applications.