Flexible electrodes for the future of light detection – Physics World

Photodetectors convert light into electrical signals and are essential in technologies ranging from consumer electronics and communications to healthcare. They also play a vital role in scientific research. Researchers are continually working to improve their sensitivity, response speed, spectral range, and design efficiency.

Since the discovery of graphene’s remarkable electrical properties, there has been growing interest in using graphene and other two-dimensional (2D) materials to advance photodetection technologies. When light interacts with these materials, it excites electrons that must travel to a nearby contact electrode to generate an electrical signal. The ease with which this occurs depends on the work functions of the materials involved, specifically, the difference between them, known as the Schottky barrier height. Selecting an optimal combination of 2D material and electrode can minimize this barrier, enhancing the photodetector’s sensitivity and speed. Unfortunately, traditional electrode materials have fixed work functions which are limiting 2D photodetector technology.

PEDOT:PSS is a widely used electrode material in photodetectors due to its low cost, flexibility, and transparency. In this study, the researchers have developed PEDOT:PSS electrodes with tunable work functions ranging from 5.1 to 3.2 eV, making them compatible with a variety of 2D materials and ideal for optimizing device performance in metal-semiconductor-metal architectures. In addition, their thorough investigation demonstrates that the produced photodetectors performed excellently, with a significant forward current flow (rectification ratio ~10⁵), a strong conversion of light to electrical output (responsivity up to 1.8 A/W), and an exceptionally high I_light/I_dark ratio of 10⁸. Furthermore, the detectors were highly sensitive with low noise, had very fast response times (as fast as 3.2 μs), and thanks to the transparency of PEDOT:PSS, showed extended sensitivity into the near-infrared region.

This study demonstrates a tunable, transparent polymer electrode that enhances the performance and versatility of 2D photodetectors, offering a promising path toward flexible, self-powered, and wearable optoelectronic systems, and paving the way for next-generation intelligent interactive technologies.

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Two-dimensional material/group-III nitride hetero-structures and devices by Tingting Lin, Yi Zeng, Xinyu Liao, Jing Li, Changjian Zhou and Wenliang Wang (2025)