Correlation between the Dipole Moment of Nonfullerene Acceptors and the Active Layer Morphology of Green-Solvent-Processed P3HT-Based Organic Solar Cells
Shreyam Chatterjee, Tatsuhiko Ohto, Hirokazu Tada, Seihou Jinnai, Yutaka Ie
Abstract
Organic solar cells (OSCs) based on poly(3-hexylthiophene) (P3HT) and nonfullerene acceptors (NFAs) have attracted steadily increasing attention due to their potential for large-scale preparation at low cost. However, irrespective of the demand for an environmentally sustainable nonhalogenated process, P3HT/NFA-based OSCs fabricated using a nonhalogenated solvent are still limited due to unclear strategies for controlling the properties of the blend film. Here, to investigate the influence of acceptor structures on the nonhalogenated green solvent process, new electron-accepting π-conjugated compounds with low dipole moments were developed for use in conjunction with nonpolar o-xylene as the nonhalogenated green solvent. The power conversion efficiencies of OSCs prepared with these new acceptors and P3HT indicated that the o-xylene-processed blend films were superior to the corresponding o-dichlorobenzene-processed and chlorobenzene-processed films. This improvement is mainly attributed to the favorable morphologies of the o-xylene-processed blend films, which are related to the good compatibility of the acceptors with o-xylene. Since P3HT possesses a low dipole moment, this study suggests that the use of a combination of an acceptor with a low dipole moment and a nonpolar green solvent is an effective approach to develop eco-friendly P3HT-based OSCs.