Attaining Infrared Detection in Devices with Narrow Bandgap Conjugated Polymers

Infrared (IR) photodetection enables applications such as biomedical imaging, environmental monitoring, industrial inspection, and more. These technologies remain dominated by inorganic semiconductors that require complex fabrication, high costs, and cryogenic cooling requirements that limit their applications within emerging technologies. Conjugated polymers offer a promising alternative offering low-cost and scalable fabrication, solution processability, room temperature operation, and many other attributes that are not available using current technologies. Here, we demonstrate how precise control of the structural and electronic properties of donor–acceptor conjugated polymers with narrow bandgaps and absorption spanning the near- to long-wave infrared (NIR-LWIR: 0.9 < λ < 15 µm), enables efficient charge photogeneration and high-performing devices that operate within these spectral regions. These solution-processable devices comprises bulk heterojunction (BHJ) photodiodes and monolithic photoconductor architectures. A key feature of BHJ materials is charge generation assisted by polymer aggregation, which is essential to compensate for the energy gap law, where non-radiative recombination rates are increased as the bandgap decreases. In contrast, single-component photoconductors can be utilized to circumvent the energy gap law in very narrow bandgap materials. Furthermore, fundamental investigations of polymer and device physics have resulted in correlations that connect intrinsic molecular features and noise with device performance, resulting in photodetectors with performance that rivals commercial inorganic systems in the IR. Collectively, these investigations have enabled new soft matter systems and device paradigms enabling optical to electrical transduction of IR light.