Solid-State Organization and Ambipolar Field-Effect Transistors of Benzothiadiazole-Cyclopentadithiophene Copolymer with Long Branched Alkyl Side Chains

Polymers

Wojciech Pisula¹  Hoi Nok Tsao¹  Dmytro Dudenko¹  Don M. Cho¹  Sreenivasa Reddy Puniredd¹  Yanfei Zhao¹  Alexey Mavrinskiy¹  Jie Shu¹  Michael Ryan Hansen¹  Martin Baumgarten¹ 

[1] Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz D-55128, Germany;

关键词: organic electronics;    ambipolar field-effect transistor;    self-assembly;    solution processing;    donor-acceptor polymer;   

DOI  :  10.3390/polym5020833

来源: mdpi

【 摘 要 】

The solid-state organization of a benzothiadiazole-cyclopentadithiophene copolymer with long, branched decyl-tetradecyl side chains (CDT-BTZ-C14,10) is investigated. The C14,10 substituents are sterically demanding and increase the π-stacking distance to 0.40 nm from 0.37 nm for the same polymer with linear hexadecyls (C16). Despite the bulkiness, the C14,10 side chains tend to crystallize, leading to a small chain-to-chain distance between lamellae stacks and to a crystal-like microstructure in the thin film. Interestingly, field-effect transistors based on solution processed layers of CDT-BTZ-C14,10 show ambipolar behavior in contrast to CDT-BTZ-C16 with linear side chains, for which hole transport was previously observed. Due to the increased π-stacking distance, the mobilities are only 6 × 10⁻⁴ cm²/Vs for electrons and 6 × 10⁻⁵ cm²/Vs for holes, while CDT-BTZ-C16 leads to values up to 5.5 cm²/Vs. The ambipolarity is attributed to a lateral shift between stacked backbones provoked by the bulky C14,10 side chains. This reorganization is supposed to change the transfer integrals between the C16 and C14,10 substituted polymers. This work shows that the electronic behavior in devices of one single conjugated polymer (in this case CDT-BTZ) can be controlled by the right choice of the substituents to place the backbones in the desired packing.

【 授权许可】

CC BY   
© 2013 by the authors; licensee MDPI, Basel, Switzerland.