Photovoltaic Effects of Dye-Sensitized Solar Cells Using Double-Layered TiO(2) Photoelectrodes and Pyrazine-Based Photosensitizers

[Image: see text] In this study, to obtain high performances of the dye-sensitized solar cells using the optimal TiO(2) photoelectrode for the synthesized pyrazine-based organic photosensitizers, three types of TiO(2) photoelectrodes were fabricated and evaluated for comparison. The double-layered nanoporous TiO(2) photoelectrode (SPD type) consisted of a dispersed TiO(2) layer and a transparent TiO(2) layer. The single-layered nanoporous TiO(2) photoelectrodes (D type and SP type) consisted of a dispersed TiO(2) layer and a transparent TiO(2) layer, respectively. The surface area, pore volume, and crystalline structures of the three types of TiO(2) 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 TiO(2) photoelectrode-adsorbed 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 TiO(2) photoelectrodes were investigated under a light intensity of 100 mW/cm(2) at AM 1.5. The DSSC device using double-layered SPD type TiO(2) photoelectrodes displayed 1.31∼2.64% efficiency, compared to single-layered SP type TiO(2) photoelectrodes (1.31∼2.50%) and D type TiO(2) photoelectrodes (0.90∼1.54%), using organic photosensitizers. The DSSC device using the SPD type TiO(2) photoelectrode and trifluoromethylbenzopyrazine (TPPF) as a photosensitizer showed the highest performances: J(sc) of 5.69 mA/cm(2), V(oc) 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 TiO(2) photoelectrodes could be interpreted from interfacial resistances according to frequency through impedance analysis.