Available online at www.pelagiaresearchlibrary.com Pelagia Research Library Advances in Applied Science Research, 2014, 5(1):8-12 ISSN: 0976-8610 CODEN (USA): AASRFC 8 Pelagia Research Library Absorbance of natural and synthetic dyes: Prospect of application as sensitizers in dye sensitized solar cell Bhim P. Kafle 1 , Babu R. Pokhrel 2 , Rajendra Gyawali 1 , Ananda. Kafle 1 , Tirtha M. Shrestha 1 , Ramita Shrestha 1 and Ravi. M. Adhikari 1 Kathmandu University, Dhulikhel, Kavre, Nepal 2 Patan Multiple Campus, Tribhuvan University, Kathmandu, Nepal 3 Angstrom Technologies, Kentuki, USA _____________________________________________________________________________________________ ABSTRACT Optical transmittance of various natural organic- and synthetic (commercial)- dyes has been measured in the wavelength range of 310-900 nm. The pure natural dye from raw samples of either flower or root of plants were extracted and dried following standard method. Then the powder of both natural and synthetic dyes were dissolved in ethanol for transmittance measurements by UV-Visible spectrometric technique. In the visible region of electromagnetic radiation, all the natural dye samples show poor absorbance, except Maharanga bicolor. While the synthetic dyes, specifically, Green-VS, Patent-Blue and Black-ADLI show strong absorbance over the wide range in the visible spectrum, demonstrating the prospect of utilizing in the fabrication of dye sensitized solar cells. Uniquely, a natural dye extracted from root of herb Maharanga bicolor shows characteristic peak at around 500 nm, associated with rovibronic transitions. Key words: absorbance, dye, Maharanga bicolor, Green VS, Patent Blue, Black ADLI, solar cell _____________________________________________________________________________________________ INTRODUCTION The conversion of solar energy to electricity utilizing solar cells represents one of the most promising and environmentally friendly methods to energy production. As a result, there have been huge efforts in a wide variety of solar cell technologies. Among the most widely used solar cells, silicon based solar cells are in the foremost. However, large-scale utilization is hindered by the production costs of solar cells, due to the rigorous process of obtaining pure silicon from silicon oxide. Thin film based dye-sensitized solar cells (DSSCs), which was first proposed by O’Breon and Gratzel in 1991, appear to be highly potential alternatives to more expensive solar cell technologies because of their high light-to-electricity conversion efficiencies, inexpensive production cost, and ease of fabrication [1]. In DSSCs, a thin film of nano-particles of metal oxide, mostly titanium oxide (TiO 2 ) or zinc oxide (ZnO), is synthesized on top of conducting glass electrode. The films of compound semiconducting material of metal oxide, which are in the order of hundreds nanometer to micro- meter thick, are sensitized by metal complex dye for absorption of light. The excited dye then releases electron, by photoelectric effect, which eventually reaches to the load via TiO 2 or ZnO nanocrystalline nanocrystals. With TiO 2 -based dye-sensitized solar cells, efficiencies of up to 11% have been obtained using standard ruthenium polypyridyl complexes as a sensitizer in the laboratory condition[1]. While, very recently, slightly improvement in efficiency (12%) was reported with the Zn porphyrin dye. Further improvements in efficiency and durability would certainly facilitate widespread utilization of this technology.