Effect of heterocycle donor in 2-cyanoacrylic acid conjugated derivatives for DSSC applications

The impact of different electron donors of 2-cyanoacrylic acid derivatives on thermal, photophysical and electrochemical properties was investigated. The synthesized compounds form donor-acceptor (D-π-A) or acceptor-donor-acceptor (A-π-D-π-A) systems. Cyanoacrylic acid moiety as an electron acceptor was linked by different π-conjugated spacers including furan, pyrrole, indole, fluorene, dibenzofuran, carbazole and phenothiazine derivatives. Density functional theory was employed to obtain optimized geometries and to calculate the frontier molecular orbital energy of the studied molecules. The selected compounds were tested as sensitizers and co-sensitizer in dye-sensitized solar cells (DSSC). The fabricated DSSC were fully characterized by the incident photon to current conversion efficiency (IPCE), current-voltage (I-V) and electrochemical impedance spectroscopy (EIS) measurements. Device with di-anchoring sensitizer based on phenothiazine core showed the highest light-to-electricity conversion efficiency of 4.85%, even higher than commercial dye N719 (4.45%). Upon co-sensitization, the DSSC made of the N719 and di-anchoring molecule with phenothiazine core lead to further enhancement of conversion efficiency up to 5.60%.