Unraveling the Molar Mass Dependence of Shearing Induced Aggregation Structure of a High Mobility Polymer Semiconductor.

Aggregation structure formation of conjugated polymers is a fundamental problem in the field of organic electronics and remains poorly understood. Herein, we thoroughly show the molar mass dependence of the aggregation structure of a high-mobility conjugated copolymer (TDPP-Se) comprising thiophene-flanked diketopyrrolopyrrole and selenophene. Five batches of TDPP-Se are prepared with number-average molecular weights (Mn ) varied greatly from 21 to 135 kg mol-1 . We combine small-angle neutron scattering and transmission electron microscopy to probe the solution structure of these polymers, consistently using a deuterated solvent. All the polymers adopt the one-dimensional (1D) rod-like aggregation structures and the radius of 1D rod is not sensitive to the Mn while the length increases monotonically with the Mn . By utilizing the ordered packing of the aggregated structure in solution, we prepare highly aligned and ordered film and thereafter realize a reliable hole mobility of up to 13.8 cm2 V-1 s-1 in organic thin-film transistors with the moderate Mn batch via bar coating. The hole mobility is among the highest values reported for diketopyrrolopyrrole-based polymers in the literature. This work paves the way to visualize the real aggregated structure of polymer semiconductors in solution state and sheds light on the aggregation structure control of high-performance electronic devices. This article is protected by copyright. All rights reserved.