A family of vertically aligned nanowires with smooth, hierarchical and hyperbranched architectures for efficient energy conversion

Abstract

A powerful full solution-based process was demonstrated to synthesize various vertically aligned TiO2 wires/rods self-assembled arrays nanostructures on conductive substrates via a simple hydrothermal growth system. Demonstrated samples included a family of high-quality and high-crystallinity anatase nanowire arrays with smooth, hierarchical or hyperbranched architectures, thanks to oriented attachment and crystallization as well as a self-assembly growth mechanism. The proposed hyperbranched arrays, consisting of long TiO2 nanowire trunks, short TiO2 nanorod branches as well as tiny TiO2 nanorod leaves (recall a tree with luxuriant foliage) and thus possessing a microscopic feature size, overcome typical shortages of insufficient dye adsorption for conventional 1D smooth nanowire arrays or prototype hierarchical nanowire arrays when applied to DSSC, which achieved for the first time similar dye uptakes (i.e. 90.10nmolcm−2vs 88.62nmolcm−2) as nanoparticle counterparts under the same thickness. Dye-sensitized solar cell fabricated with an ~8μm long novel hyperbranched nanowire arrays photoelectrode yields an impressive power conversion efficiency (PCE) of 8.11%, which was much greater than that of anatase TiO2 nanoparticle (20nm in diameter) counterpart due to synergistic effects of high dye uptakes and superior broadband light scattering for improved light harvesting as well as fast charge transport for efficient charge collection for the former.