Titanium dioxide nanowires modified tin oxide hollow spheres for dye-sensitized solar cells
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unctional Oxides Research Letter
Titanium dioxide nanowires modified tin oxide hollow spheres for dye-sensitized solar cells Yajie Wang, Chengbin Fei, Rong Zhang, and Lixue Guo, Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences , Beijing 100083, China; National Center for Nanoscience and Technology (NCNST), Beijing 100083, China Ting Shen, and Jianjun Tian, Advanced Material and Technology Institute, University of Science and Technology, Beijing 100083, China Guozhong Cao, Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences , Beijing 100083, China; National Center for Nanoscience and Technology (NCNST), Beijing 100083, China; Department of Materials and Engineering, University of Washington, Seattle, WA 98195-2120, USA Address all correspondence to Guozhong Cao at [email protected] and Jianjun Tian at [email protected] (Received 24 June 2016; accepted 22 August 2016)
Abstract Tin oxide (SnO2) hollow spheres modified with titanium dioxide (TiO2) nanowires (NWs) synthesized by sequential hydrothermal reactions were investigated as photoanodes for dye-sensitized solar cells. Not only does the hydrothermal treatment form numerous short TiO2 NWs on the surface of SnO2 spheres, but also passivates the surface of SnO2. Consequently, the specific surface area of the photoanode and dye loading are almost doubled, at the same time the surface defects and charge recombination are both appreciably reduced. As a result, the short-circuit photocurrent density and open-circuit photovoltage both greatly increased. The power conversion efficiency of the solar cells increases from 0.4% to 2.9%.
Introduction Since titanium dioxide (TiO2) nanoparticles first has been combined with dye molecules to fabricate low-cost photovoltaic device in 1991, dye-sensitized solar cells (DSCs) have attracted extensive interest in the past few decades as a promising candidate to convert solar energy to electricity.[1–3] Although using TiO2 nanoparticle films with collaborated silyl-anchor and carboxy-anchor dyes has achieved a power conversion efficiency of higher than 14% in 2015,[4] TiO2 as photoanodes in DSCs still face many challenges.[5,6] It has become a focus recently that looking for alternative metal oxide semiconductors with wide band gap and good photoelectrochemical properties.[7–10] ZnO nanostructures for DSC applications has shown that they can offer large specific surface areas with well-controlled morphologies, direct electron pathways with much higher electron mobility, and also can reduce the combination rate when the surface defects are properly controlled.[11–13] Tin oxide (SnO2) as a promising alternative semiconductor has many advantages for DSCs: (1) good electron mobility, indicating electron transport fast in photoanodes and (2) large band gap (3.6 eV) and more-negative conduction band minimum, which can enhance the light harvesting in the near-infrared spectral region when combined with small band gap sensitizer.[14] Many different nanostructures of SnO2 have been
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