Requirements for Forming Efficient 3-D Charge Transport Pathway in Diketopyrrolopyrrole-Based Copolymers: Film Morphology vs Molecular Packing.
To achieve extremely high planarity and processability simultaneously, we have newly designed and synthesized copolymers composed of donor units of 2,2'-(2,5-dialkoxy-1,4-phenylene)dithieno[3,2-b]thiophene (TT-P-TT) and acceptor units of diketopyrrolopyrrole (DPP). These copolymers consist of a highly planar backbone due to intramolecular interactions. We have systematically investigated the effects of intermolecular interactions by controlling the side chain bulkiness on the polymer thin-film morphologies, packing structures, and charge transport. The thin-film microstructures of the copolymers are found to be critically dependent upon subtle changes in the intermolecular interactions, and charge transport dynamics of the copolymer based field-effect transistors (FETs) has been investigated by in-depth structure-property relationship study. Although the size of the fibrillar structures increases as the bulkiness of the side chains in the copolymer increases, the copolymer with the smallest side chain shows remarkably high charge carrier mobility. Our findings reveal the requirement for forming efficient 3-D charge transport pathway and highlight the importance of the molecular packing and interdomain connectivity, rather than the crystalline domain size. The results obtained herein demonstrate the importance of tailoring the side chain bulkiness and provide new insights into the molecular design for high-performance polymer semiconductors.
Department of Chemical Engineering, Pohang University of Science and Technology , San31, Nam-gu, Pohang, Gyoungbuk 37673, South Korea.
Gang-Young
GY
Lee
Department of Chemical Engineering, Pohang University of Science and Technology , San31, Nam-gu, Pohang, Gyoungbuk 37673, South Korea.
A-Reum
AR
Han
Department of Chemical Engineering, Pohang University of Science and Technology , San31, Nam-gu, Pohang, Gyoungbuk 37673, South Korea.
Taewan
T
Kim
Department of Chemical Engineering, Pohang University of Science and Technology , San31, Nam-gu, Pohang, Gyoungbuk 37673, South Korea.
Hae Rang
HR
Lee
Department of Chemical Engineering, Pohang University of Science and Technology , San31, Nam-gu, Pohang, Gyoungbuk 37673, South Korea.
Joon Hak
JH
Oh
Department of Chemical Engineering, Pohang University of Science and Technology , San31, Nam-gu, Pohang, Gyoungbuk 37673, South Korea.
Taiho
T
Park
charge transport; field-effect transistors; microstructure; organic electronics; polymer semiconductors