Synthesis of novel star-shaped truxene cored small molecules and applications in organic solar cells

The synthesis of two new star-shaped organic small molecules with a truxene core, molecules 11 and 12, were carried out. They varied in sidechain length with molecule 11 having hexahexyl and molecule 12 having hexadodecyl side chains. The physical and photovoltaic properties were measured and characterized. Both molecules showed activity in UV-visible light and electrochemical processes. Molecule 11 had optical and electrochemical HOMO-LUMO energy gaps of 2.15 and 2.45 eV, respectively, while molecule 12 had 2.12 and 2.50 eV gaps. Photovoltaic device fabrication and testing revealed bifunctional acceptor-donor properties of the molecules in bulk-heterojunction organic solar cells. The device PCEs for molecule 11 were 0.003% and 0.002%, while the PCEs for 12 were 0.004% and 0.03%. This improvement was attributed to the ease of processing and self-assembly induced by the long alkyl side chains of molecule 12.