Controlling Conjugation and Solubility of Donor-Acceptor Semiconducting Copolymers for High-Performance Organic...

Diketopyrrolopyrrole (DPP)-based copolymers, including poly[2,5-bis(2-octyldodecyl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione-(E)-1,2-di([2,2'-bithiophen]-5-yl)ethene] (PDDBE) and poly[2,5-bis(2-octyldodecyl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione-(E)-1,2-bis(6-hexylthieno[3,2-b]thiophen-2-yl)ethene] (PDTTE), were synthesized by alternating a DPP-derivative acceptor (A) block with different donor (D) blocks, such as (E)-1,2-di([2,2'-bithiophen]-5-yl)ethene (DBE) and (E)-1,2-bis(6-hexylthieno[3,2-b]thiophen-2-yl)ethene (TTE). As solution-processed semiconducting channel layers in organic field-effect transistors (OFETs), PDDBE and PDTTE copolymers had drastically different ordered structures on polymer-grafted SiO2 dielectrics. Multiple-layered domains of PDDBE had a long-range, π-conjugated extension but a wide π-stacking distance, d(010), of 3.90 Å. One-dimensional nanorod-percolated agglomerates of PDTTE had a much shorter d(010) of 3.71 Å, originating from the alternating A-D structures of the DPP derivative with different D blocks. The corresponding ordered domains yielded a wide range of field-effect mobilities from 0.01 to 1.40 cm2 V(-1) s(-1) in the OFETs.