Kirk J Ziegler
University of Florida, USA
Title: Controlling electron recombination in nanowire-based DSSCs
Biography
Biography: Kirk J Ziegler
Abstract
Electron recombination in dye-sensitized solar cells (DSSCs) results in significant electron loss and performance degradation. To our knowledge, the reduction of electron recombination via blocking layers in nanowire-based DSSCs has never been investigated. In this study, HfO2 or TiO2 blocking layers are deposited on nanowire surfaces via atomic layer deposition (ALD) to reduce electron recombination in nanowire-based DSSCs. The control cell consisting of ITO nanowires coated with a porous shell of TiO2 by TiCl4 treatment yields an efficiency of 2.82%. The efficiency increases dramatically to 5.38% upon the insertion of a 1.3 nm TiO2 compact layer between the nanowire surface and porous TiO2 shell. This efficiency enhancement implies that porous sol-gel coatings on nanowires (e.g., via TiCl4 treatment) result in significant electron recombination in nanowire-based DSSCs while compact coatings formed by ALD are more advantageous because of their ability to act as a blocking layer. While the insertion of a high band-gap compact layer of HfO2 between the interface of the conductive nanowire and TiO2 shell improves performance, a comparison of the cell performance between TiO2 and HfO2 compact layers indicates that charge collection is suppressed by the difference in energy states. Consequently, the use of high band-gap materials at the interface of conductive nanowires and TiO2 is not recommended.
