Low-Bandgap Near-IR Conjugated Polymers/Molecules for Organic Electronics

The study emphasizes the correlation between chemical structures, physical properties, and resulting device performance of the solution-processed polymers/small molecules, and tries to provide a comprehensive understanding from materials design to a variety of device applications. To achieve near-IR absorbing/emitting abilities, strong donor-acceptor interaction and stabilization of the quinoid resonant structure are required. However, due to the smaller one-dimensional quantum well length, bandgap lowering is more difficult and normally requires very strong donor or acceptor units in the case of small molecules. Anthopoulos and Patil showed that the triethylene glycol side chain can enhance molecular self-assembly and increase the FET mobility for DPP-based polymers. Gong applied PS-TPD-PFCB, a commonly used electron-blocking material in light-emitting diodes, in a novel IR photodetector and realized very low dark current and high detection sensitivity. Yang and Li's recent work shows a clear link between the polymers' molecular compatibility (preferred orientations) and the resulting multidonor system morphology, which has a profound impact on the carrier transport and device efficiency.