Improved structural order by side-chain engineering of organic small molecules for photovoltaic applications

Despite obvious progress in organic semiconducting material design and organic bulk-heterojunction solar cell power conversion efficiencies the rationalization of the molecular design to finely tune organic semiconductor properties is still challenging. Herein, thanks to a particular dumbbell-shaped molecular design allowing partial decoupling between the structural properties and the frontier energy level positioning and optical absorption properties, we demonstrate the impact of the nature of side chains along the conjugated backbone on the structural properties of conjugated molecules. Thus, linear side chains on the structurally cohesive triazatruxene building blocks of our molecules provide higher stacking abilities, resulting in higher charge transport abilities and photovoltaic performances. These dumbbell-shaped molecules are a promising molecular family for reaching high solar cell efficiencies as well as for understanding in detail the impact of chemical structure on optoelectronic properties.