Research On High-efficient Dye-sensitized Solar Cells Based On Titanium Substrates

Dye-sensitized solar cells (DSSCs) have recently emerged as a cost-effective alternative to conventional silicon photovoltaics owing to their eco-friendly and simple fabrication process, and low manufacturing cost. Flexible DSSCs, based on either plastics or metal foils as conductive substrates, demonstrate various applications and have great potential in future photovoltaic market. Titanium (Ti) foils have been widely used in flexible in light of their advantages, like low sheet resistance, good flexibility, superior corrosion and high-temperature resistances, etc. In this paper, highly efficient smalland large-scale flexible DSSCs based on Ti substrates, for either photoanode or counter electrode, were investigated systematically.Firstly, using chemically treatments, morphology variations of Ti surface as well as the photovoltaic improvement of the flexible DSSCs were investigated in detail. When Ti substrate was treaed with acid, H2O2, andTiCl4, a double-layer structured photoanode was constructured, in which the top-layer and the under-layer were composed of TiO2nanoparticles (thickness600nm) and TiO2nanoforest (thickness200nm), respectively. Based on this construction, high conversion efficiencies of up to8.46%of the all-flexbile DSSCs have been obtained. It was confirmed that the TiO2nanoforest under-layer had some positive effects in dye loading, charge transfer, electron collectionas well as suppressing charge recombination, et al. Besides, a high efficiency of7.8%was obtained of the same type DSSC with a low-cost and easily prepared P25paste.Secondly, an excellent Ti/Pt counter electrode was prepared by treating Ti substrate with acid, exhibiting a comparable catalytic activity to the traditional rigid counter electrode of sputtering FTO/Pt. After screening several atmospheres, it was found that N2protection for sintering was necessary since if sintered under air, TiOx thin layer was formed and unfavorable to collection of electrons by external circuit. Using this Ti-based counter electrode into DSSCs, a high efficiency of8.81%was yielded, higher than that based on traditional FTO/Pt counter electrode.Finally, a large-scale all-flexible DSSC with an active area of2.7cm2was prepared. A high efficiency of6%was obtained and the photovoltic performance was stable in the durability test of over1000hours. Moreover, three types of Ti-based DSSC with an active area of16.2cm2were prepared. The photoconversion efficiencies of Ti/TiO2+ITO/PEN/Pt, Ti/TiO2+FTO/Pt and FTO/TiO2+Ti/Pt were4.73%,4.58%and4.76%, respectively.