Dye-sensitized nanocrystalline CdS and ZnS solar cells with different organic dyes
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Said A. El-Sherbieny National Institute of Laser, Cairo University, Giza, Egypt (Received 8 February 2009; accepted 7 July 2009)
We have developed dye-sensitized nanocrystalline CdS and ZnS solar cells (DSSCs) based on crystal violet, methylene blue, and fluorescein photosensitizers. Nanocrystalline CdS and ZnS were synthesized by a green synthesis method using starch as the capping agent. Characterization of nanocrystalline CdS and ZnS was carried out by optical absorption and x-ray diffraction. The results indicate that CdS and ZnS prepared by this method may be used as photoelectodes in photo-electro-chemical energy conversion systems. DSSCs have been built and their photocurrent, open-circuit voltage, fill factor, and efficiency have been measured under direct sunlight illumination (1000 Wcm2). The efficiency of the cells made from dye-CdS was much higher than that of the cells made from dye-ZnS. This can be attributed to the particle size effect. Among the prepared dye-sensitized solar cells, a DSSC based on fluorescein dye as the photosensitizer produced the highest overall light solar energy to electricity conversion efficiency.
I. INTRODUCTION
Recent research on solar cells has been aimed at lowering the fabrication cost to decrease the price of the energy obtained.1 In this context, suitable materials should be easily preparable, inexpensive, and show stable behavior over long periods of operation. For these reasons, electrochemical photovoltaic cells composed of dye-sensitized oxides have been widely investigated. Gra¨tzel and others have demonstrated that Ru-dye sensitized titantium dioxide (TiO2) offers a respectably high solar energy-toelectricity conversion efficiency of up to 10%.2 This raised the hope of fabricating a stable, highly efficient, electrochemical photovoltaic cell. Nanocrystalline metal sulfides such as ZnS and CdS are promising materials in this respect.3 They are used in a variety of applications, such as optical and optoelectronic devices, photocatalysis,4 and window layers for fabrication of solar cell, due to their high transmittivity and low resistivity.5 Several methods were documented for the synthesis of nanocrystalline CdS and ZnS. Some of these methods are metal-organic precursors, sol-gel, sonochemical, microwave assisted synthesis, and chemical bath deposition.6 In this paper we present our study on the synthesis and characterization of CdS and ZnS in nanocrystalline form to prepare the photoelectrochemical solar cell. On the other hand, there are few studies on the sensitization of a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2010.0077
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http://journals.cambridge.org
J. Mater. Res., Vol. 25, No. 3, Mar 2010 Downloaded: 28 Feb 2015
the nanocrystalline semiconductor electrode by organic dyes compared to those of metal complex.7 Therefore, this paper focuses on the sensitization of these metal sulfides with various organic dyes. II. EXPERIMENTAL A. Preparation of ZnS and CdS nanoparticles
The green synthesis method usin
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