Iodine-free solid-state dye-sensitized solar cells with fullerene derivatives as hole transporting materials

This study focuses on the syntheses of N,N-dimethyl-2-thiophenyl-3,4-fulleropyrrolidium iodide (DMFPI), poly N-methyl-2-thiophenyl-3,4-fulleropyrrolidine-co-3-hexylthiophene (MFP-co-3HT), poly N-methyl-2-thiophenyl-3,4-fulleropyrrolidine-co-3-dodecylthiophene (MFP-co-3DT), and poly N-methyl-2-thiophenyl-3,4-fulleropyrrolidine-co-3-thiopheneacetic acid (MFP-co-3TA) and their photovoltaic properties as hole transporting materials (HTMs) for use in DSSCs. The synthesized DMFPI and copolymers were characterized by 1H NMR, MALDI TOF-mass spectrometry, UV–vis spectroscopy, and cyclic voltammetry. The DSSC devices were fabricated and their photovoltaic performances were measured using a solar simulator under AM 1.5 illumination.

► We focused on DSSCs based on soluble fullerene derivatives as the HTM.
► They have proper levels for the transfer of the hole charges.
► The charge transfer resistances were decreased by introducing DMFPI without I2.
► The good charge transfer ability of them led to increase the Jsc values.
► The Jsc values were led to an improvement in their efficiency.