Multilayer Assembly of Nanowire Arrays for Dye-Sensitized Solar Cells

Vertically ordered nanostructures synthesized directly on transparent conducting oxide have shown great promise to overcome the limitations of current dye-sensitized solar cells (DSCs) based on random networks of nanoparticles. Synthesis of such structures with a high internal surface area, however, has been challenging. Here we demonstrate a convenient process for synthesizing multilayer assemblies of ZnO nanowire arrays and using the assemblies for fabrication of DSCs. The assembled multilayer ZnO nanowire arrays possess an internal surface area that is more than five times larger than what one can possibly obtain with single-layer nanowire arrays. DSCs fabricated using such multilayer arrays yield a power conversion efficiency of 7%, which is comparable to TiO2 nanoparticle-based DSCs. The ordered structure with a high internal surface area opens up opportunities for further improvement of DSCs by using solid-state electrolytes and kinetically fast redox couples.