Poor manʹs green bulk heterojunction photocells: A chlorine-free solvent for poly(3-hexylthiophene)/C60 composites

Although C60 is unquestionably not only the cheapest but also the most energy-saving fullerene, lack of suitable solvent to make bulk heterojunction composites with it has prevented its use in photocells. Here, it is shown that a not-so-common organic solvent 1,2,4-trimethylbenzene (TMB) is useful to prepare cost-effective bulk heterojunction composites based on C60. Additionally, chlorine-free TMB is expected to be environmental friendly compared with chloroaromatic solvents commonly used for the preparation of polymer/fullerene composites. A preliminary evaluation indicated that a poly(3-hexylthiophene) (P3HT)/C60 bulk heterojunction photocell prepared from TMB solution shows power conversion efficiency comparable to that of a P3HT/PCBM photocell, suggesting that C60 should be revisited as a promising candidate for an acceptor material in polymer bulk heterojunction composites for low-cost green photocells.