Effect of architectures assembled by one dimensional ZnO nanostructures on performance of CdS quantum dot-sensitized solar cells

Effect of ZnO architectures on photoelectric conversion efficiency of CdS quantum dot-sensitized ZnO solar cells is investigated. Four kinds of architecture assembled by one dimensional ZnO nanostructures, including ZnO nanorod arrays, nanotube arrays, forest, and pyramid arrays formed by thin nanowires, are designed and fabricated as photoanodes. Light-to-electricity conversion efficiency of these cells is 1.60% for the pyramid arrays, 1.34% for the forest, 1.08% for the nanotube arrays and 0.50% for the nanorod arrays, respectively, indicating that the architecture strongly affects the photoelectric conversion efficiency. Absorption spectra, dark current curves and photoelectron decay are measured to analyze the causes of differences. We find that light absorption and photoelectron transmission from ZnO nanostructures to FTO substrate are important factors for the cells. As the ZnO pyramid arrays formed by thin nanowires have anti-reflection character, high specific area for deposition of CdS sensitizer and fast photoelectron transmission channels to FTO substrate, higher photoelectric conversion efficiency is achieved. This investigation is important to the improvement on conversion efficiency for quantum dot-sensitized solar cells.