Dielectric constant engineering of organic semiconductors: effect of planarity and conjugation length

Jiang, W. et al. (2022) Dielectric constant engineering of organic semiconductors: effect of planarity and conjugation length. Advanced Functional Materials, 32(3), 2104259. (doi: 10.1002/adfm.202104259)

Abstract

Bulk heterojunction organic solar cells continue to show steady photoconversion efficiency improvements. However, single component organic solar cells are a particularly attractive alternative due to the relative simplicity of device manufacture. It has been proposed that organic semiconductors with a high dielectric constant (≈10) could give rise to spontaneous free charge carrier generation upon photoexcitation. In this manuscript, factors are explored that affect the dielectric constant of organic semiconductors, particularly the optical-frequency dielectric constant. The properties of monomers, dimers and trimers of two isoelectronic families of materials that have acceptor units composed of one or two dicyanovinylbenzothiadiazole moieties and one to three donor units are compared. The donor components are composed of either fluorenyl or cyclopentadithiophene moieties with the same glycol-based solubilizing groups. It is found that chromophore planarity and orientation with respect to the substrate, and film density affect the optical and electronic properties of the materials, especially the high-frequency dielectric constant. The results also indicate that delocalization of the highest occupied and lowest unoccupied molecular orbitals is a critical factor. The dimer with two dicyanovinylbenzothiadiazole moieties and two dithienocyclopentadiene units is found to have the highest optical frequency dielectric constant and overall performance.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Loch, Dr Alex
• Authors: Jiang, W., Jin, H., Babazadeh, M., Loch, A. S., Raynor, A., Mallo, N., Huang, D. M., Jiao, X., Liang Tan, W., McNeill, C. R., Burn, P., and Shaw, P. E.
• College/School: College of Science and Engineering > School of Chemistry
• Journal Name: Advanced Functional Materials
• Publisher: Wiley
• ISSN: 1616-301X
• ISSN (Online): 1616-3028
• Published Online: 11 August 2021
• Copyright Holders: Copyright © 2021 Wiley-VCH GmbH
• First Published: First published in Advanced Functional Materials 32(3):2104259
• Publisher Policy: Reproduced in accordance with the copyright policy of the publisher