Theoretical investigation on the photophysical properties of low-band-gap copolymers for photovoltaic devices

Geometrical parameters, electronic structures and photophysical properties of some new [2,1,3]-benzothiadiazole based alternating copolymers, have been investigated through Density Functional Theory (DFT) calculations. The theoretical results including structural characteristics and photovoltaic properties of these compounds are in good agreement with the available experimental data extracted from bibliography. The Time-Dependent Density Functional Theory (TDDFT) level is employed to investigate the excited singlet states in donor-acceptor and donor-pi spacer-acceptor structures. From these results, the correlation structure-properties is better understood. Furthermore, the benzothiadiazole-based composite, which is blended with fullerene derivative [6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM), seems to be a good active layer in bulk heterojunction solar cells. (C) 2011 Elsevier B.V. All rights reserved.