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International Journal of Photoenergy
Volume 2015 (2015), Article ID 708048, 7 pages
http://dx.doi.org/10.1155/2015/708048
Research Article

Structural Dependence of Electronic Properties in A-A-D-A-A-Type Organic Solar Cell Material

Department of Polymer Science, The University of Akron, Akron, OH 44325, USA

Received 27 October 2014; Accepted 12 January 2015

Academic Editor: David Worrall

Copyright © 2015 Ram S. Bhatta and Mesfin Tsige. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Small conjugated molecules (SCMs) are promising candidates for organic photovoltaic (OPV) devices because of their structural simplicity, well control over synthetic reproducibility, and low purification cost. However, industrial development of SCM-based OPV devices requires improving their performance, which in turn relies on the fundamental understanding of structural dependence of electronic properties of SCMs. Herein, we report the structural and electronic properties of the BCNDTS molecule as a model system for acceptor-acceptor-donor-acceptor-acceptor (A-A-D-A-A) type SCMs, using density functional theory (DFT) and time-dependent DFT methods. Systematic calculations of two-dimensional potential energy surfaces, molecular electrostatic potential surfaces, ground state frontier molecular orbital energies, and the vertical excitation energies are performed. We found that the lowest energy conformation of the BCNDTS molecule is planar. The planar conformation favors the lowest ground state and the excited state energies as well as the strongest oscillator strength. The present results suggest that SCMs containing central dithienosilole cores connected with 2,1,3-benzothiadiazole groups have potential to be an efficient electron donor for OPV devices.