Mobility Evaluation of [1]Benzothieno[3,2‑b][1]benzothiophene Derivatives: Limitation and Impact on Charge Transport

Wawrzinek, Robert; Sobus, Jan; Chaudhry, Mujeeb Ullah; Ahmad, Viqar; Grosjean, Arnaud; Clegg, Jack K.; Namdas, Ebinazar B.; Lo, Shih-Chun

Abstract

Amongst contemporary semiconductors many of the best performing materials are based on [1]benzothieno[3,2-b][1]benzothiophene (BTBT). Alkylated derivatives of these small molecules not only provide high hole mobilities but can also be easily processed by thermal vacuum or solution deposition methods. Over the last decade numerous publications have been investigating molecular structures and charge transport properties to elucidate what makes these molecules so special. However, the race towards ever higher mobilities resulted in significantly deviating values, which exacerbates linking molecular structure to electronic properties. Moreover, a recently arisen debate on overestimation of organic field-effect transistor mobilities calls for a revaluation of these numbers. We synthesised and characterised four BTBT derivatives with either one or two alkyl chains (themselves consisting of either eight or ten carbon atoms), and investigated their spectroscopic, structural and electrical properties. By employing two probes, gated 4-point probe and gated van der Pauw measurements we compare field effect mobility values at room and low temperatures and discuss their feasibility and viability. We attribute mobility changes to different angles between molecule planes and core-to-core double layer stacking of asymmetric BTBT derivatives and show higher mobilities in the presence of more and longer alkyl chains. A so called “zipper effect” brings BTBT cores in closer proximity promoting stronger intermolecular orbital coupling and hence higher charge transport.

Citation

Wawrzinek, R., Sobus, J., Chaudhry, M. U., Ahmad, V., Grosjean, A., Clegg, J. K., …Lo, S. (2019). Mobility Evaluation of [1]Benzothieno[3,2‑b][1]benzothiophene Derivatives: Limitation and Impact on Charge Transport. ACS Applied Materials and Interfaces, 11(3), 3271-3279. https://doi.org/10.1021/acsami.8b16158

• Journal Article Type: Article
• Acceptance Date: Dec 24, 2018
• Online Publication Date: Dec 24, 2018
• Publication Date: Jan 23, 2019
• Deposit Date: Jan 8, 2019
• Publicly Available Date: Dec 24, 2020
• Journal: ACS Applied Materials and Interfaces
• Print ISSN: 1944-8244
• Electronic ISSN: 1944-8252
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 11
• Issue: 3
• Pages: 3271-3279
• DOI: https://doi.org/10.1021/acsami.8b16158