Modifying electronic properties of ICBA through chemical substitutions for solar cell applications

Abstract

Fullerene derivatives are the most widely used type of acceptor material in the organic solar cells (OSCs) active layers, but there are still some problems to be overcome, such as increased solubility and adjustment of the frontier electronic levels for a better combination with the donor materials in the active layer. Chemical modification of the materials already employed in active layers is an interesting way to vary the electronic properties in order to find new materials, because it is possible, in principle, to tune the intrinsic properties of the material aiming to improve the solar cell efficiency. Thus, we studied theoretically the effect caused by chemical substitutions on the electronic properties of the ICBA, one of the fullerene derivatives employed in OSCs. Geometry optimizations and electronic structure data were obtained by DFT/PBE/6-311G(d,p) calculations for 13 ICBA derivatives. We show that by chemical substitutions of ICBA, it is possible to modify the energies of the frontier electronic levels, increase the solubility, and find new derivatives that show improvements in open circuit voltage and morphology of the active layer, potentially bringing better efficiency for OSCs.