Ultrafast Highly Sensitive Self-Powered MSIM Photodetector Based on Organic Semiconductor/Dielectric Interfaces for Broadband Visible to Near-Infrared Communication

The growing importance of high-speed and energy-efficient photodetectors in broadband communication has sparked widespread interest in organic materials owing to their tunable optical characteristics and ease of production. However, this Schottky-type organic photodetector (OPD) has low detectivity and a high dark current, requiring additional voltage biasing. Herein, the development of a highly sensitive self-powered OPD with metal-semiconductor-insulator-metal (MSIM) structure (ITO/PEDOT:PSS/Organic photoactive layer/dielectric/silver) is presented, using polymer PM6, acceptor Y6, and its blend with parylene as a dielectric layer for broadband spectral detection spanning the visible to near-infrared (NIR) range at high speeds. Such a new class of devices can produce fast transient photocurrent signals with opposite polarity both under light ON/OFF cycles in response to pulsed optical stimuli, which makes the signals inherently more distinguishable. The detailed transient photocurrent measurements are performed for fabricated MSIM OPD with different illumination conditions at various operational frequencies, and the PM6:Y6-based devices are found to be most sensitive compared to the single-component devices due to increased charge generation and accumulation without voltage biasing. Further, the faster response time (approximate to nanosecond) of both the positive and negative peaks with a remarkably high cutoff frequency of 5.6 MHz outperformed most of the state-of-the-art OPD. The extraordinary performance of the MSIM photodetector demonstrated by the real-time NIR communication of various ASCII codes suggests its potential for infrared communication. The tunable polarity of the signal offers a novel platform for next-generation transient-type MSIM photodetectors, enhancing their detectivity and response time without the need for additional biasing across a wide range of applications.