Systematic Investigation of Solution-State Aggregation Effect on Electrical Conductivity in Doped Conjugated Polymers

The mesoscopic solution-state aggregation plays a dominant role in the multilevel self-assembly of conjugated polymers. However, its effect on solid-state microstructures and the electrical performance of conjugated polymers is still a puzzle due to the limitation of characterization techniques. Herein, we have developed four isoindigo-based conjugated polymers with varied alkyl chains to reveal the relationship between solution-state aggregation, molecular doping process, and charge transport properties. For the solution-state aggregation, the photophysical and microstructural characterizations were adopted to explore the solvated aggregation structures of these four polymers, where well-differentiated aggregate sizes were observed. IIDDT-C3 showed small solvated aggregate sizes but excellent aggregate connectivity in solutions. The characterization of the solid-state microstructure demonstrated that IIDDT-C3 had ideal crystalline solid-state microstructures with densely fibrillar morphology, which endowed IIDDT-C3 with the highest electrical conductivity up to 531 +/- 50 S cm(-1) after doping among these four polymers. Our work provides molecular guidance for clarifying the structure-performance relationship between aggregation structures and the electrical properties of the doped conjugated polymers with different alkyl chains. [GRAPHICS] .

Automated summary

This study developed four isoindigo-based conjugated polymers to investigate the relationship between solution-state aggregation, molecular doping process, and charge transport properties. The characterization revealed that one of the polymers, IIDDT-C3, exhibited the highest electrical conductivity due to its well-differentiated aggregate sizes and excellent aggregate connectivity in solutions.