Photovoltaic Effects of Dye-Sensitized Solar Cells Using Double-Layered TiO2 Photoelectrodes and Pyrazine-Based Photosensitizers

In this study, to obtain high performances of the dye-sensitized solar cells using the optimal TiO2 photoelectrode for the synthesized pyrazine-based organic photosensitizers, three types of TiO2 photoelectrodes were fabricated and evaluated for comparison. The double-layered nanoporous TiO2 photoelectrode (SPD type) consisted of a dispersed TiO2 layer and a transparent TiO2 layer. The single-layered nanoporous TiO2 photoelectrodes (D type and SP type) consisted of a dispersed TiO2 layer and a transparent TiO2 layer, respectively. The surface area, pore volume, and crystalline structures of the three types of TiO2 photoelectrodes were analyzed by Brunauer-Emmett-Teller method, field-emission scanning electron microscopy, and X-ray diffractometry to confirm their crystallinity and surface morphology. The structures of the three types of TiO2 photoelectrodeadsorbed organic sensitizers were investigated using X-ray photoelectron spectroscopy. The photovoltaic performances of DSSC devices using three organic photosensitizers adsorbed onto the three types of TiO2 photoelectrodes were investigated under a light intensity of 100 mW/cm2 at AM 1.5. The DSSC device using double-layered SPD type TiO2 photoelectrodes displayed 1.31 similar to 2.64% efficiency, compared to single-layered SP type TiO2 photoelectrodes (1.31 similar to 2.50%) and D type TiO2 photoelectrodes (0.90 similar to 1.54%), using organic photosensitizers. The DSSC device using the SPD type TiO2 photoelectrode and trifluoromethylbenzopyrazine (TPPF) as a photosensitizer showed the highest performances: Jsc of 5.69 mA/cm2, Voc of 0.69 V, FF of 0.67, and efficiency of 2.64%. The relationship between photovoltaic effects and interfacial resistance characteristics of DSSCs using the three organic photosensitizers adsorbed onto the three types of TiO2 photoelectrodes could be interpreted from interfacial resistances according to frequency through impedance analysis.

Automated summary

In this study, three types of TiO2 photoelectrodes were fabricated and evaluated for the dye-sensitized solar cells using synthesized organic photosensitizers. The double-layered nanoporous TiO2 photoelectrode showed the highest efficiency, compared to the single-layered nanoporous TiO2 photoelectrodes. The relationship between photovoltaic effects and interfacial resistance characteristics could be interpreted from impedance analysis.