Applying strong external electric field to thiophene‐based oligomers: A promising approach to upgrade semiconducting performance. Issue 5 (26th November 2016)

• Record Type: Journal Article
• Authors: Zhan, Xiaoling; Shi, Hu; Liu, Hongguang; Lee, Jin Yong
• Is Part Of: Journal of computational chemistry. Volume 38:Issue 5(2017)
• Page Start: 304
• Page End: 311
• Publication Date: 2016-11-26
• Subjects: oligothiophenes -- reorganization energy -- external electric field -- charge transport -- density functional theory; Chemistry -- Data processing -- Periodicals; 542.85
• DOI: 10.1002/jcc.24684
• Languages: English
• ISSNs: 0192-8651

Abstract

Abstract : A key parameter dictating the rate of charge transfer (CT) is reorganization energy ( λ ), an energy associated with geometry changes during hole/electron transfer. We show that "ironing" the inter‐ring dihedral angles of oligothiophenes via proper substitutions or insertions (e.g., ‐OR, ‐F or ‐C≡C‐), decreases the λ and thus promotes CT according to Marcus equation. Our results demonstrate, to attain a smaller λ, extending oligomer length is only significant if the flattened backbone structure is realized. Of great interest is that external electric fields, which are ubiquitous in electronic devices yet commonly overlooked in the computation of λ, can have a significantly greater impact than conventional substitutions. It is important to emphasize, the responses of λ to external fields is system‐dependent. Compared to fused‐ring conjugated systems, single‐bond connected thiophenes are more sensitive to external fields. Fx lowers the λ (552 meV) of quaterthiophene by almost 80% at the intensity of 1 V/Å, down to a value (125 meV) which is even lower than that of pentacene (154 meV) and rubrene (219 meV) at the same level of theory. © 2016 Wiley Periodicals, Inc. Abstract : This work is conducted to grasp the power of external electric fields, which could be utilized to address the challenges associated with organic semiconductors. Oligothiophenes with planarized backbone structures that exhibit attractive properties, such as exceptionally low reorganization energies that are favorable for intermolecular hole transfer, are investigated upon application of external electric fields.