Quinoxaline-functionalized C60 derivatives as electron acceptors in organic solar cells

Two novel C-60 derivative acceptors (2,3-bis(5-tert-butylthiophen-2-yl)-6,7-dimethylquinoxaline-C-60-monoadduct (TQMA) and 2,3-bis(5-tert-butylthiophen-2-yl)-6,7-dimethylquinoxaline-C-60-bisadduct (TQBA)) with high LUMO levels have been synthesized and employed as model systems to study their interactions with donor poly(3-hexylthiophene) (P3HT) in bulk heterojunction organic solar cells (BHJ-OSCs). The optoelectronic, electrochemistry and the subsequent photovoltaic properties of these two acceptors have been fully investigated. Although the power conversion efficiency remains to be improved, BHJ-OSCs incorporating P3HT as donor and TQMA (or TQBA) as acceptor exhibit an open-circuit voltage (V-OC) of 0.76 V (or 0.84 V), which is about 0.12 V (or 0.20 V) higher than PCBM as electron acceptor. The different photovoltaic performance among these acceptors can be rationalized by their different LUMO energies and molecular packing.