Soluble porphyrin donors for small molecule bulk heterojunction solar cells

This paper describes the rational design of porphyrin donors for application in solution-processed small molecule bulk heterojunction (BHJ) solar cells. The porphyrin donors were designed to possess high solubility and strong intermolecular interactions, via the appropriate selection of peripheral substituents: these molecules bear tetraethynyl porphyrin cores with two aromatic and two aliphatic groups in a trans manner. We have also demonstrated the substitution effect on the aromatic groups: energy levels, solubility and film morphology were significantly modified by the substituents, which consequently influenced the efficiencies of the solar cells as well. After optimization, the device based on [5,15-bis(phenylethynyl)-10,20-bis[(triisopropylsilyl)ethynyl]porphyrinato] magnesium(II) (2):PC60BM showed a PCE of 2.5%.