Molecular design for all-in-one self-assembled donor–acceptor organic solar cells

Abstract

The stability of organic solar cells still remains one of the main challenges to make this technology suitable for large scale mass production. The stability of the morphology is one main degradation channel in currently used bulk heterojunction systems. We introduce three different all-in-one donor–acceptor amphiphilic triads and perform molecular dynamics simulations in order investigate the stacking of the donor and acceptor sub-molecules after performing a simulated annealing step. We show that the molecular volume of each sub-molecule of the triad plays an important role for the stability of the π -stacking within the bilayer sheet. Further, we found that TIPS-pentacene and TIPS-tetraazapentacene sub-molecules serving as donor and acceptor, respectively, keep their crystalline nature in the bilayer sheet. Thus, by such a system, charge carrier mobilities in the range of 1 cm 2 /Vs should be possible, which is three orders of magnitude higher compared to measured mobilities in existing highly efficient organic solar cells. Therefore, by this approach not only the stability can be increased, but also the fill factor and therefore the power conversion efficiency can be improved.