(397x) Fabricating Ultra-High Density Nanowires for Dye-Sensitized Solar Cells

Fabricating Ultra-High Density Nanowires for Dye-Sensitized Solar Cells

Cheng Xu^1,*, Yang Zhao¹, Jie Liu¹, and Kirk J. Ziegler¹

¹Department of Chemical Engineering, University of Florida at Gainesville, 1006 center drive, Gainesville, FL 32611, US

*Presenting Author (Ph: 352-392-3122; Email: chengotopia@ufl.edu)

Abstract

            Dye-sensitized solar cells (DSSCs) use titania nanoparticles as the photoanode and have been extensively studied for the past decade as a promising technology for low-cost, high-performance solar cells. However, ever since the efficiency of DSSCs reached 11% in 2001, little progress has been made in efficiency due to energy loss from the random walk of electrons and the recombination with defects and surface trap sites that result in slow trap-limited electron diffusion in the titania nanoparticles. A ZnO core-shell nanowire network offers unique advantages over the traditional nanoparticle-based DSSCs. By eliminating the random walk of electrons and the loss mechanism from interfacial charge recombination and back reactions, improvements are observed in the charge injection at the interface and electron diffusion within ZnO nanowires. However, it is still challenging to fabricate these nanowires with similar surface area as the nanoparticle system. In this study, anodized alumina (AAO) is used as a template to control the density and dimension of nanowires. Multiple growth methods are used to grow highly crystalline ZnO nanowires, including hydrothermal, chemical vapor deposition (CVD), electrodeposition, and vapor-liquid-solid (VLS) methods. These vertically aligned nanowires can also be transferred onto a foreign flexible transparent substrate. The impact of nanowire dimensions on DSSC performance is investigated to obtain a better understanding of the impact of photoanode morphology on charge transport dynamics. Comparisons of a theoretical model and experimental observations can help understand how to control interfacial charge transfer, leading to significant improvements to DSSC efficiency due to the ultra-high photoactive surface area in these nanowire systems.