Highly uniform and vertically aligned SnO2 nanochannel arrays for photovoltaic applicationsElectronic supplementary information (ESI) available. See DOI: 10.1039/c5nr00202h

Nanostructured electrodes with vertical alignment have been considered ideal structures for electron transport and interfacial contact with redox electrolytes in photovoltaic devices. Here, we report large-scale vertically aligned SnO 2 nanochannel arrays with uniform structures, without lateral cracks fabricated by a modified anodic oxidation process. In the modified process, ultrasonication is utilized to avoid formation of partial compact layers and lateral cracks in the SnO 2 nanochannel arrays. Building on this breakthrough, we first demonstrate the photovoltaic application of these vertically aligned SnO 2 nanochannel arrays. These vertically aligned arrays were directly and successfully applied in quasi-solid state dye-sensitized solar cells (DSSCs) as photoanodes, yielding reasonable conversion efficiency under back-side illumination. In addition, a significantly short process time (330 s) for achieving the optimal thickness (7.0 μm) and direct utilization of the anodized electrodes enable a simple, rapid and low-cost fabrication process. Furthermore, a TiO 2 shell layer was coated on the SnO 2 nanochannel arrays by the atomic layer deposition (ALD) process for enhancement of dye-loading and prolonging the electron lifetime in the DSSC. Owing to the presence of the ALD TiO 2 layer, the short-circuit photocurrent density ( J sc ) and conversion efficiency were increased by 20% and 19%, respectively, compared to those of the DSSC without the ALD TiO 2 layer. This study provides valuable insight into the development of efficient SnO 2 -based photoanodes for photovoltaic application by a simple and rapid fabrication process. Highly uniform and vertically aligned SnO 2 nanochannel arrays are applied in quasi-solid state dye-sensitized solar cells as photoanodes.