Enhancement of Solar Efficiency of Dye-Sensitized Solar Cell by Molecular Engineering of Organic Dye Incorporating N-alkyl Attached 1, 8-Naphthalamide Derivative
Controlling orientation of dye molecules adsorbed on TiO2 surface needs extensive attention for improving the photovoltaic parameters of dye-sensitized solar cells (DSSCs). Suppression of charge recombination and self-aggregation of dye molecules on TiO2 surface also plays a vital role in the improvement of cell efficiency. In this report, based on the bi-anchoring structure containing N-alkyl attached 1, 8-naphthalamide derivative as a donor system and spiroBiproDOT as a π-spacer, an organic dimeric dye (D-Dye) was designed and synthesized by incorporating Suzuki coupling followed by Knoevenagel condensation. The maximum power conversion efficiency of 7.1 % with a Voc and Jsc of 0.70 V and 14.6 mA/cm2, respectively, was achieved for the DSSC employing D-Dye. A monomeric dye (M-Dye) was also synthesized and the resultant cell efficiency achieved 4.85 % with Voc and Jsc of 0.67 V and 9.93 mA/cm2, respectively, which was 33% lower than that of its dimeric analogue (D-Dye). Photo-physical experiment was carried out for both organic dyes to understand their light absorption characteristics. Incident-photon to current conversion efficiency (IPCE) and electrochemical impedance measurements were also performed to rationalize the better photovoltaic performance of DSSCs employing the dimeric D-Dye, which was due to effective suppression of charge recombination and self-aggregation of dye molecules. Co-adsorption of D-Dye (0.4 mM) with N-719 (0.4 mM) in a ratio of 10:1 (D-Dye: N-719) v/v further enhanced the cell efficiency to 8.34 % (Voc of 0.77 V and Jsc of 14.9 mA/cm2).