Optimization of dye adsorption time and film thickness for efficient ZnO dye-sensitized solar cells with high at-rest st
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NANO EXPRESS
Open Access
Optimization of dye adsorption time and film thickness for efficient ZnO dye-sensitized solar cells with high at-rest stability Wei-Chen Chang1,2, Chia-Hua Lee2, Wan-Chin Yu1* and Chun-Min Lin1
Abstract Photoelectrodes for dye-sensitized solar cells were fabricated using commercially available zinc oxide (ZnO) nanoparticles and sensitized with the dye N719. This study systematically investigates the effects of two fabrication factors: the ZnO film thickness and the dye adsorption time. Results show that these two fabrication factors must be optimized simultaneously to obtain efficient ZnO/N719-based cells. Different film thicknesses require different dye adsorption times for optimal cell performance. This is because a prolonged dye adsorption time leads to a significant deterioration in cell performance. This is contrary to what is normally observed for titanium dioxide-based cells. The highest overall power conversion efficiency obtained in this study was 5.61%, which was achieved by 26-μm-thick photoelectrodes sensitized in a dye solution for 2 h. In addition, the best-performing cell demonstrated remarkable at-rest stability despite the use of a liquid electrolyte. Approximately 70% of the initial efficiency remained after more than 1 year of room-temperature storage in the dark. To better understand how dye adsorption time affects electron transport properties, this study also investigated cells based on 26-μm-thick films using electrochemical impedance spectroscopy (EIS). The EIS results show good agreement with the measured device performance parameters. Keywords: Zinc oxide, Dye-sensitized solar cells, Dye adsorption time, Film thickness, Conversion efficiency, At-rest stability, Electrochemical impedance spectroscopy
Background Dye-sensitized solar cells (DSSCs) are regarded as promising low-cost solar cells with high light-toenergy conversion efficiency. Systems based on titanium dioxide (TiO2) nanoparticle films sensitized with ruthenium (Ru)-based dyes have achieved a light-toenergy conversion efficiency of more than 11% [1,2]. Other metal oxides, including tin dioxide, indium (III) oxide, niobium pentoxide, and zinc oxide (ZnO), have also been used as photoelectrode materials [3-5]. Among these materials, ZnO has attracted considerable attention because it has an energy-band structure similar to that of TiO2 but possesses a higher electron mobility and allows more flexibility in synthesis and morphologies [6,7]. * Correspondence: [email protected] 1 Institute of Organic and Polymeric Materials, National Taipei University of Technology, Taipei 10608, Taiwan Full list of author information is available at the end of the article
The photovoltaic performance of a DSSC relies on the characteristics of its photoanode, which plays a central role in converting light into electrical energy. A DSSC photoanode typically consists of a mesoporous oxide film on a transparent conducting glass substrate. Dye molecules that capture photons from light during device operation are attached t
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