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Taming Charge Transport in Semiconducting Polymers with Branched Alkyl Side Chains
Author(s) -
Schroeder Bob C.,
Kurosawa Tadanori,
Fu Tianren,
Chiu YuCheng,
Mun Jaewan,
Wang GingJi Nathan,
Gu Xiaodan,
Shaw Leo,
Kneller James W. E.,
Kreouzis Theo,
Toney Michael F.,
Bao Zhenan
Publication year - 2017
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201701973
Subject(s) - materials science , polymer , alkyl , side chain , charge carrier , organic field effect transistor , chemical physics , electron mobility , chemical engineering , polymer chemistry , field effect transistor , nanotechnology , transistor , optoelectronics , organic chemistry , chemistry , composite material , electrical engineering , voltage , engineering
The solid‐state packing and polymer orientation relative to the substrate are key properties to control in order to achieve high charge carrier mobilities in organic field effect transistors (OFET). Intuitively, shorter side chains are expected to yield higher charge carrier mobilities because of a denser solid state packing motif and a higher ratio of charge transport moieties. However our findings suggest that the polymer chain orientation plays a crucial role in high‐performing diketopyrrolopyrrole‐based polymers. By synthesizing a series of DPP‐based polymers with different branched alkyl side chain lengths, it is shown that the polymer orientation depends on the branched alkyl chain lengths and that the highest carrier mobilities are obtained only if the polymer adopts a mixed face‐on/edge‐on orientation, which allows the formation of 3D carrier channels in an otherwise edge‐on‐oriented polymer chain network. Time‐of‐flight measurements performed on the various polymer films support this hypothesis by showing higher out‐of‐plane carrier mobilities for the partially face‐on‐oriented polymers. Additionally, a favorable morphology is mimicked by blending a face‐on polymer into an exclusively edge‐on oriented polymer, resulting in higher charge carrier mobilities and opening up a new avenue for the fabrication of high performing OFET devices.