Design of dye-sensitized solar cells with new light-harvesting dyes

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ABSTRACT Phthalocyanine dyes are well known for their intense absorption in the red and near-IR regions. We synthesized novel phthalocyanines for dye-sensitized solar cell (DSSC). Those dy es can absorb in the red an d near-IR regions and adsorb onto the surface of TiO 2 . Using such phthalocyanines as working electrode with TiO 2 , DSSCs were assembled and its photocurrent-voltage and IPCE characteristics have been studied and compared. Light energy conversion efficiency of DSSCs depended on the structures of phthalocyanine, the co-adsorbent, and the electrolytes. Furthermore, multi-dye type DSSC was investigated, which mixed a phthalocyanine and a carotenoid derivative. The conversion efficiency of the multi-dye DSSC increased compared with the DSSC which used single dye. Keywords: Dye-sensitized solar cell, Phthalocyanine, Light-harvesting 1. INTRODUCTION In nature, photosynthetic membrane enables the highly effici ent energy conversion from light to chem ical energy [1]. Numerous dye molecules are incorporated within the photosynthetic membrane and arranged by the protein molecules [2, 3]. The spatial arrangement of dye molecules within the membra ne results in the high efficiency of energy conversion. The study of molecular assembly of using chlorophyll, carotenoid, porphyrin, and phthalocyanine derivatives can be useful as a model of the natural photon-electron conversion [4-8]. The mechanism of dye-sensitized solar cell (DSSC) is similar to natural photosynthesis where the conversion is carried out by the photo-induced electron transfer of natural dyes. The inorganic solar cells have good conversion efficiency, but they are high-cost, heavy weight, and some based on highly toxic material. Even if the conversion efficiency of DSSCs are still low, DSSCs have marked advantages, light-weight, cost-effective, toxic-free and scalable [9, 10]. A DSSC c onsists of nano-crystalline titanium oxide (TiO