The power conversion efficiency of organic solar cells (OSCs) could benefit from systematic studies to improve bulk heterojunction (BHJ) morphology by modifying donor compounds. Supramolecular self-assembly is an attractive strategy to combine the beneficial properties of polymeric donors, such as a well-controlled morphology, with the homogeneous composition of small molecule donors for OSCs. We report here on two tripodal "star-shaped" small-molecule donor compounds based on diketopyrrolopyrrole (DPP) side chains for solution-processed BHJ OSCs. The tripod molecules were found not to aggregate in solution or form crystalline domains in thin films when a branched alkyl chain (2-ethylhexyl) substituent was used, whereas linear (docedecyl) alkyl chains promote the formation of one-dimensional (1D) nanowires and more crystalline domains in the solid state. We demonstrate that the 1D self-assembly of these tripods enhances the performance of the corresponding solution-processed OSCs by 50%, which is attributed to the significant increase in the fill factor of devices resulting from a reduction of trap states.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films