Pyrrolic Polysquaraine: A Promising Polymer Semiconductor for Short-Wavelength Infrared Organic Photodetector and Imager
Short-wavelength infrared (SWIR) organic photodetectors (OPDs) have attracted considerable attention due to their potential to overcome the limitations of inorganic counterparts. However, developing organic semiconductors with strong SWIR detection remains a significant challenge. Herein, we design and synthesize a new conjugated pyrrolic polysquaraine (PSQ-COT) by integrating a pyrrolic squaraine unit with a strong electron-donating moiety, achieving an absorption onset extending to 1.2 μm. To evaluate its detection performance, we fabricated two types of PSQ-COT-based SWIR OPDs with PC61BM and BTP-eC9 as the electron acceptors, respectively. The resulting PSQ-COT:PC61BM OPD exhibited superior detection performance compared with the BTP-eC9 counterpart, achieving an impressive specific detectivity of 1.08 × 10^12 Jones at 1030 nm under zero bias. This enhanced performance is due to the lower degree of energetic disorder and reduced trap density in the PSQ-COT:PC61BM device. Furthermore, we successfully integrated the PSQ-COT:PC61BM OPD into a high-pixel-density image array (640 × 512 pixels), enabling clear matter identification under SWIR light irradiation. This work provides valuable insights into designing high-performance organic semiconductors for SWIR light detection and imaging applications.