The present invention relates to new fullerene derivatives of formulae 1a-d, 2 and 3: method of synthesizing said derivatives, and applications thereof in organic photovoltaics, e.g., organic solar cells. In particular, the fullerene derivatives of the present invention are soluble in non-halogenated solvents such that an environmental-friendly and low-cost fabrication method for industrialization of solar cell based on the new fullerene derivatives is provided. An ink formulation for forming a thin film on a substrate of organic photovoltaics comprising at least one of the fullerene derivatives of the present invention is also provided. Greater than 3% power conversion efficiency of the organic solar cells (area=0.16 cm2) formed based on the fullerene derivatives of the present invention with less pollution and lower cost in fabrication can be achieved in the present invention.