Ladder-Type π-Conjugated Polysquaraines for Near-Infrared Organic Photodetectors
Jin He, Zhi Wang, Yerun Gao, Bijin Xiong, Ming Shao, Zhong’an Li
Abstract
Near-infrared organic photodetectors (NIR OPDs) have gained widespread attention due to the rapidly growing demand for portable, lightweight, and low-cost sensors. However, the development of high-performance NIR organic semiconductors remains challenging. Herein, we report two new ladder-type conjugated pyrrolic polysquaraines simply prepared by polycondensation, namely, PSQ-IDT and PSQ-IDTT, which exhibit narrow optical band gaps of 1.26 and 1.28 eV, respectively. Both polysquaraines have good compatibility with the PC 61 BM acceptor, and the resulting NIR OPDs exhibit a wide detection range covering 400–1000 nm. We demonstrate that the fused ring bridge has a critical effect on the optical and electronic properties of polysquaraines by regulating the polymer backbone geometry. As a result, the PSQ-IDT OPD offers a better photodetection performance than PSQ-IDTT, with specific detectivity over 10 11 Jones in 400–1000 nm under the self-powered mode and fast response rise and fall times of 3.9 and 3.5 μs, making it a good material candidate for NIR OPDs.