Synthesis and characterization of a novel fullerene derivative for use in organic solar cells

A novel fullerene derivative with an N-hexylphenothiazine moiety, PTZ-C60, was synthesized and characterized. The new synthesized fullerene showed good solubility in common organic solvents such as toluene, chlorobenzene and 1, 2 dichlorobenzene. The synthetic product PTZ-C60 was characterized by 1H and 13C NMR, FT-IR and UV–vis spectroscopy. Photovoltaic devices were fabricated using the new fullerene derivative as the electron acceptor and P3HT as the electron donor. The configuration of the device was as follows: ITO/PEDOT:PSS/active layer/LiF/Al. The weight ratios of the electron donor to the acceptor in the active layer were 1:0.5, 1:0.7, and 1:1. The open-circuit voltage (Voc) of the fabricated devices was found to be higher than that of devices based on C60 because the LUMO energy level of the new fullerene derivative was higher than that of C60. Further, the power conversion efficiency (PCE) of these devices was observed to be high when annealing was carried out at 150 °C for 5 min and the thickness of the active layer was 80 nm. The maximum Voc, short-circuit current density, and PCE of the best device were 0.608 V, 4.393 mA/cm2, and 1.29%, respectively.