PEDOT Nanotube Arrays as High Performing Counter Electrodes for Dye Sensitized Solar Cells. Study of the Interactions Among Electrolytes and Counter Electrodes

TiO 2 electrodes and dye sensitization : The general procedure for the preparation of the DSC devices, according to a sandwich-type structure, consisted in a double TiO 2 layer deposited on glass/FTO (Pilkington TEC15, ∼ 15 Ω /sq resistance) using the Screen printing technique. The resulting photo-electrodes were sintered at 450 ºC and then immersed into a 0.04M TiCl 4 solution for 30 min at 70 ºC followed by calcination at 450 ºC for 30 min to obtain good electrical contact between the nanoparticles. After cooling to 40 ºC, the electrodes were immersed into the dye solutions overnight. Two sets of electrodes were employed depending on the electrolyte used. For set A, the TiO 2 electrodes were prepared with a 12 μ m thick (HT/SP Solaronix) + 7 μ m thick scatter layer (WER4_O Dyesol), the photoelectrodes were sensitized for 24 hours in a N719 dye solution (0.5 mM N719 and 0.5mM of chenodeoxycholic acid as a coadsorbent in acetonitrile/tert-buthanol 1/1 (v/v)). For set B, the electrodes were prepared with a 8 μ m thick (18NR-T Dyesol 20 nm) + 4 μ m thick scatter layer (WER4_O Dyesol), sensitized for 16 hours in a dye solution (0.5 mM N719 in acetonitrile/tert-butanol (v/v = 1:1)). After the adsorption of the dye on the TiO 2 fi lms, the working electrodes were rinsed with the same solvent used for the dye solution. μ m thick). The electrolyte was introduced though a hole previously drilled into the working electrode and sealed afterwards. In all these cells the hole was not in the CE as in normal cells in order to avoid damage of the PEDOT fi lm. The hole was introduced into the working electrode, before the deposition of the titania fi lm. The prepared solar cells had a 0.2 cm 2 area, the masking solar cell 0.125 cm 2 . and cell characterization : The morphology of the samples was analyzed using a Scanning Electron Microscope (JSM-5500LV). J–V curves were measured using a solar simulator equipped with a 1000W ozone-free Xenon lamp and AM 1.5 G fi lter (Oriel), and the light intensity was adjusted according to an NREL-calibrated Si solar cell with a KG-5 fi lter to one-sun intensity (100 mW cm − 2 ). IS measurements were carried out under same illumination conditions than J–V curves, and different bias potentials that ranged from zero to open circuit voltage and frequencies between 1 MHz and 0.1 Hz, with an AC perturbation of 20 mV. Measurements were carried out with cell positioned on a refl ecting metallic surface.