Preparation Of Flexible Dye-sensitized Solar Cell Photoanode

The selection of flexible dye sensitized solar cells (DSSCs) working electrodematerials has a big impact to performance of photovoltaic devices. Wide band-gapnanocrystalline TiO2films can absorb more dye because of high surface area.Decreased adhesion of the TiO2film with the substrate and poor electrical contactbetween TiO2particles are the difficulties when plastic substrates are used due to lowtemperature processing. Compared with TiO2nanoparticles, one-dimensional TiO2nanomaterials are suggested to be superior in electrical performance due to its uniquechannel for carrier transportation and may improve the performance of photovoltaicdevices such as flexible dye-sensitized solar cells. The key point of further improvingits performance and expanding its application is to change and modifiy its structure.Based on this research background, in this work, we fabricated TiO2nanoparticalesand nanotubes flexible working electrodes. The application of the two kinds ofnanostructured materials in photovoltage devices has been extensively studied.1．Our work used the ball-milling technique to prepare well dispersed TiO2slurries and graphene oxide (GO) was added into TiO2nanoparticles pastes as anauxiliary binder. The highest energy conversion efficiency1.12%was achieved forthe1wt%GO-P25mixture. P25decorated with GO can increase the films dyeadsorption due to the existence of GO in TiO2paste could help to get crackfreemesoporous TiO2films. Excessive amounts of graphene oxide will affect the dyeabsorption of light, block the electrons transport channel so that decrease theefficiency.2．In this work, free-standing TiO2nanotube arrays were prepared by two-stepelectrochemical anodization of titanium foils, the length of the nanotube wascontrolled by anodic time, then the TiO2nanotube arrays were transferred to a flexibleITO/PEN substrate using titania slurries, which may realize the fabrication of thefront-illuminated flexible DSSCs to improve the light absorption and the photovaltaicperformance. The flexible DSSC with20μm nanotube membrane show theshort-circuit current density (Jsc) of7.35mA/cm2, open-circuit voltage (Voc) of668mV, fill factor (FF) of0.680and energy conversion efficiency (η) of3.44%,respectively. The conversion efficiency and short-circuit current density increase by 11.7%and7.6%for the20μm nanotube membrane if comparing with30μmnanotube membrane, respectively. UV-Vis, IPCE characterization methods show thatphotoelectric performance increases with the increasing length of the nanotube arrays,the higher defect densities in the TiO2nanotube arrays with30μm length will act asthe recombination center for the transportation of the photo-induced electrons, and itmay cause the dark current and decrease the photo-current in the solar cells.3．The conical TiO2nanotube membrances have been successfully prepared byadjusting the applied voltage during the two-step anodic oxidation process. Thecrystal structures, morphologies and optical absorption properties of the samples arecharacterized by XRD, TEM, UV-Vis. For comparison of the14μm nanotube arraysit is seen that the photovoltaic performance for the conical tubes (3.78%) is higherthan that of the cylinder tubes (2.90%) by28.6%. The reason of the enhancedphotovoltaic performance is due to the enhanced light-harvesting ability of theconical TiO2nanotube arrays.