Solution‐Processable Unsymmetrical Triarylamines: Towards High Mobility and ON/OFF Ratio in Bottom‐Gated OFETs

Self‐assembly of organic small molecules into an ordered thin film has been the key strategy towards efficient charge transport for organic field‐effect transistors (OFETs). Solution processing is a feasible and economic way to enhance pi–pi interaction. Herein, nitrile‐substituted unsymmetrical tri...

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Bibliographic Details
Published in:Chemistry : a European journal 2019-11, Vol.25 (66), p.15155-15163
Main Authors: Dheepika, Ramachandran, Mohamed Imran, Predhanekar, Bhuvanesh, Nattamai S. P., Nagarajan, Samuthira
Format: Article
Language:English
Subjects:
Assembly
Carrier mobility
Charge transport
Chemical reactions
Chemistry
Coupling (molecular)
Cross coupling
Crystal structure
Current carriers
Field effect transistors
Mobility
organic field-effect transistors
self-assembly
solution processing
Solvents
Switches
Thin films
triarylamines
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Summary:Self‐assembly of organic small molecules into an ordered thin film has been the key strategy towards efficient charge transport for organic field‐effect transistors (OFETs). Solution processing is a feasible and economic way to enhance pi–pi interaction. Herein, nitrile‐substituted unsymmetrical triarylamines for OFET applications with high mobility are reported. The compounds were constructed by Suzuki cross‐coupling reactions under inert conditions. The HOMO level of about 5.3 eV indicates good hole‐transporting ability. OFETs were assembled in bottom‐gate, top‐contact architecture. Devices fabricated from a binary solvent system exhibited excellent p‐channel characteristics, with impressively high charge‐carrier mobility of up to 2.58 cm2 V−1 s−1 and ION/OFF current ratios of 106–107. SEM and AFM analysis showed the efficient molecular self‐assembly attained by the simple and effective solvent‐engineering method. Theoretical insights obtained by DFT calculations supported by single‐crystal structures showed that the crystalline nature and packing modes of these compounds ensure high mobility. The results prove that these compounds have great potential for use in numerous electronic applications, such as sensors and logic switches. TAA OFETs: A series of nitrile‐substituted triarylamines (TAAs) was developed for use as solution‐processable organic field effect transistors (OFETs). The CN group was introduced to alter the twist and tilt angles of TAA and thus attain an unsymmetrical structure. TAA‐based devices exhibited pronounced p‐channel behavior with high charge‐carrier mobility and large ON/OFF current ratio (see scheme).
ISSN:0947-6539
1521-3765
DOI:10.1002/chem.201903450