In this study, photoelectrodes composed of a porous layer of 100-nm ZnO particles are fabricated for use in dye-sensitized solar cells. The electrodes are immersed in an aqueous TiCl 4 solution to coat them with a thin layer of TiO 2 for preparation of ZnOTiO 2 coreshell electrodes. This simple treatment drastically improves the cell performance, resulting in the highest obtained efficiency of 3.91%. This efficiency is higher than that of 100-nm TiO 2 particle cells.To date, dye-sensitized solar cells (DSSCs) have been able to achieve 11% solar energy conversion efficiency.13 Although such performance makes DSSCs a viable substitute for amorphous silicon solar cells for use in some electronic devices, it is still necessary to further increase the efficiency of DSSCs so that their use can be scaled to provide energy on the order of gigawatts. 4 For this, technological breakthroughs in terms of better materials are required to advance the development of DSSCs to the next generation. Most photoelectrode technology is based on porous titanium(IV) oxide (TiO 2 ) semiconductor layers. On the other hand, there are some reports of the application of other metal oxides such as tin(IV) oxide (SnO 2 ), niobium(V) oxide (Nb 2 O 5 ), and zinc oxide (ZnO) as the main material for photoelectrodes and for covering material on TiO 2 core particles as a coreshell structure. 5,6 In particular, ZnO has a band gap and energy level of the conduction band edge similar to those of TiO 2 and has an electron diffusion coefficient higher than that of TiO 2 .7,8 Furthermore, ZnO crystals can be synthesized and grown in mild conditions, and their morphology can be easily controlled by synthetic conditions. These characteristics make it very suitable for use as the porous semiconductor layer in DSSCs.916 Keis et al. used 150-nm spherical ZnO particles as the semiconductor layer in photoelectrodes and compressed the ZnO layer in order to deposit on the conductive substrate at room temperature. 15 The cells exhibited 5.0% efficiency under 0.1 sun illumination. Moreover, the highest efficiency of 6.58% in ZnO cells was also reported by Saito and Fujihara. 17 These results indicate that ZnO is a promising photoelectrode material. Nevertheless, the performance of ZnO cells is still considerably inferior to that of TiO 2 cells, especially in terms of fill factor (FF) and open-circuit voltage (V oc ). Carrier recombination in ZnO may be the reason for their inferior performance. 18 In addition, ZnO is chemically unstable and is easily dissolved in acidic and basic solutions. Further, its dyeloading capacity is less than that of TiO 2 . One of the possible solutions to these shortcomings is to cover the ZnO with a stable material. Law et al. covered ZnO nanowires with thin layers of TiO 2 and Al 2 O 3 by atomic layer deposition (ALD) and obtained a high V oc of over 800 mV. 18 Recently, electrodes composed of aggregated ZnO nanoparticles were also covered by TiO 2 using the same ALD techniques, and the obtained efficiency was 6%.However, V oc and FF...

An active oxygen generator system using UV irradiation and ozone aeration was developed. The purpose of this study was to decompose benzoic acid using the active oxygen generator. The product of decomposition reaction was measured by UV absorption spectrum, and was analyzed by FT-IR. This active oxygen generator was confirmed to decompose benzoic acid effectively.