DFT and TD-DFT study on the structural and optoelectronic characteristics of chemically modified donor-acceptor conjugated oligomers for organic polymer solar cells

College

College of Science

Department/Unit

Chemistry

Document Type

Article

Source Title

Polymer

Volume

97

First Page

55

Last Page

62

Publication Date

8-5-2016

Abstract

© 2016 Elsevier Ltd. All rights reserved. The structural and optoelectronic properties of several substituted poly[N-9′-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole) (PCDTBT) conjugated oligomers have been investigated by density functional theory (DFT) and time-dependent density functional theory (TD-DFT). Various electron-withdrawing and electron-donating groups were attached to the 5′ position of the benzothiadiazole unit in the PCDTBT oligomers. HOMO energies (EHOMO), LUMO energies (ELUMO), and the fundamental energy gaps (EGap) were calculated using DFT while the first singlet excited states (EOpt) were calculated using TD-DFT. Results show that the structural properties of the oligomers greatly affect the optoelectronic properties. Results also show that both electron-withdrawing and electron-donating groups are capable of lowering the EGap of PCDTBT. Several properties of substituted PCDTBT, which may affect the solar cell properties, were then calculated and compared with the calculated values for PCDTBT. From the calculated properties, PCDTBT-F showed improvement in the EGap, open-circuit voltage (VOC), and ionization potential (IP), which may lead to solar cells with improved power conversion efficiency (PCE) compared to PCDTBT.

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Digitial Object Identifier (DOI)

10.1016/j.polymer.2016.05.025

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