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

Issue Date

8-2016

Abstract

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.

Source or Periodical Title

Polymer

ISSN

0032-3861

Volume

97

Page

55-62

Document Type

Article

Physical Description

illustrations, tables, graphs

Language

English

Subject

Density functional theory, Optoelectronic properties, PCDTBT

Identifier

https://doi.org/10.1016/j.polymer.2016.05.025.

Digital Copy

yes

Link to Full Text

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