Pyrrolic polysquaraine: a promising polymer semiconductor for <?A3B2 pi6?>short-wavelength infrared organic photodetector and imager

Short-wavelength infrared (SWIR) organic photodetectors (OPDs) have recently 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 × 1012 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.