Abstract
Surface modification of porous ZnO photoelectrode using one- and two-step etching process is investigated for enhancing power conversion efficiency of ZnO dye-sensitized solar cells. ZnO films are modified by the diluted NH4OH solutions for one-step etching process and used as photoelectrode of dye-sensitized solar cells. Rough porous films are observed after one-step etching process. The fabricated cells based on the optimized one-step etched films show a significant increase in short-circuit current density. The short-circuit current density is directly changed with amount of dye adsorption, which is related to specific surface area. The etched films exhibit higher specific surface area over two times than nonetched films. Thus, the large specific surface area is the key success for increasing amount of dye adsorption. Internal electrochemical property of fabricated cells is also improved, indicating that chemical surface of ZnO films is modified in the same time. The DSSCs fabricated on two-step etched films with NH4OH and mixed acid HCl : HNO3show the maximum power conversion efficiency of 2.26%. Moreover, fill factor is also increased due to better redox process because of the formation of fine porous structure during the etching process. Therefore, these results implied that the roles of etching processes are improving specific surface area and fine porous formation which can provide better dye adsorption and redox process for dye-sensitized solar cell application.
Highlights
Dye-sensitized solar cell (DSSC) is one of the attractive solar cells over the past two decades due to various advantages such as relative high efficiency, easy and simple fabrication process on both rigid and flexible substrates, and nontoxicity, low cost, and environmental friendly raw materials [1, 2]
Power conversion efficiency of ZnO dye-sensitized solar cell fabricated on modified photoelectrode is enhanced due to high specific surface area, which is supported by the fine porous structure
High specific surface area is the major factor for increasing dye adsorption to enhance power conversion efficiency of DSSC
Summary
Dye-sensitized solar cell (DSSC) is one of the attractive solar cells over the past two decades due to various advantages such as relative high efficiency, easy and simple fabrication process on both rigid and flexible substrates, and nontoxicity, low cost, and environmental friendly raw materials [1, 2]. Photoelectrode is considered to be an effective component of DSSC in PCE enhancement due to a key role in controlling photoconversion process such as dye adsorption, light scattering, charge separation, and electron transportation [6,7,8]. To improve the photoconversion process, surface modification of photoelectrode has been successfully applied for PCE enhancement by using various techniques. Surface modification of porous ZnO photoelectrode using one- and two-step etching process is investigated for enhancing power conversion efficiency of ZnO dyesensitized solar cells. Wet chemical etching process of diluted base (NH4OH) solutions in distilled water is a promising simple process to improve specific surface area of ZnO photoelectrode, and mixed acid solution of HCl : HNO3 in distilled water is used to form fine porous structure. Power conversion efficiency of DSSC is expected to be enhanced by the optimized condition
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