2018/11/21 by Jing He, He, Jing, Xiaoqing Kong +9
Physics and Astronomy · #Applied Physics (physics.app-ph) #FOS: Physical sciences #Soft Condensed Matter (cond-mat.soft) #cond-mat.soft #physics.app-ph
paper · pdf · doi:10.48550/arxiv.1811.08924
34 pages, 5 figures and 8 supplemental figures
arxiv created 2018/11/21 · arxiv updated 2018/11/26
Through a combination of rheological characterization and temperature-variable imaging methods, a novel gelation pathway in dilute solutions of a semiconducting polymer to achieve interconnected, crystalline networks with hierarchical porosity is reported. Upon rapid cooling, solutions of regioregular poly(3-hexylthiophene) (RR-P3HT) in ortho-dichlorobenzene formed thermoreversible gels. Temperature-variable confocal microscopy revealed cooling-induced structural rearrangement to progress through viscoelastic phase separation. The phase separation process arrested prematurely during the formation of micron-sized solvent-rich "holes" within the RR-P3HT matrix due to intrachain crystallization. Cryogen-based scanning electron microscopy of RR P3HT gels revealed the existence of an interfibrillar network exhibiting nano-sized pores. Remarkably, these networks formed to equal gel strengths when a third component, either small molecule phenyl C61 butyric acid methyl ester (PCBM) or non-crystallizing regiorandom (Rra)-P3HT, was added to the solution. Organic solar cells in which the active layers were deposited from phase-separated solutions displayed 45% higher efficiency compared to reference cells.