Diels-Alders adducts of C60 and esters of 3-(1-indenyl)-propionic acid: alternatives for [60]PCBM in polymer:fullerene solar cells

A series of new, easily synthesized C-60-fullerene derivatives is introduced that allow for optimization of the interactions between rr-P3HT and the fullerene by systematic variation of the size of the ester group. Two compounds gave overall cell efficiencies of 4.8%, clearly outperforming [60]PCBM which gives 4.3% under identical conditions.