Aggregation Behavior and Electrical Performance Control of Isoindigo-Based Conjugated Polymers via Carbosilane Side Chain Engineering
Chenhui Xu, Zhongli Wang, Weijia Dong, Chunyong He, Yibo Shi, Junhua Bai, Chan Zhang, Mengyuan Gao, Hanqiu Jiang, Yunfeng Deng, Long Ye, Yang Han, Yanhou Geng
Abstract
Side chains of conjugated polymers (CPs) have played a vital role in the regulation of solution processibility and semiconducting performance. Herein, carbosilane side chains, which manifest the advantages of low-cost and facile synthesis as compared to the common alkyl ones, were employed to regulate the aggregation behaviors and charge transport properties of isoindigo-based polymers. Three polymers, IIDSiC12, IIDSiC8, and IIDC12, with carbosilane side chains of varying bulkiness and alkyls as the control were synthesized via direct arylation polymerization. Anisotropic one-dimensional pre-aggregates of different aspect ratios were developed in solution, as disclosed by solution small-angle neutron scattering, which further determined the order of the microstructure in bar-coated films for organic thin-film transistors (OTFTs). It is noteworthy that the relatively large radius (20.5 Å) and moderate aspect ratio (∼20) of IIDSiC12 solution aggregates ensured a solid-state microstructure of the highest order, as evidenced by well-aligned fiber-like morphology and the largest range of packing order. As a result, OTFTs based on IIDSiC12 achieved the maximum saturation electron mobility up to 4.10 cm2 V–1 s–1 with a reliability factor of 81%, which is among the highest mobilities of n-type CPs. The results reported here may encourage the easier synthesis of high mobility CPs using the carbosilane side chain engineering.