How Does Back-Reaction at the Conducting Glass Substrate Influence the Dynamic Photovoltage Response of Nanocrystalline Dye-Sensitized Solar Cells?

Abstract

In dye-sensitized nanocrystalline solar cells (DSC), the transfer of electrons from the conducting glass substrate to triiodide ions in solution is an important loss mechanism that can be suppressed by using thin compact blocking layers of TiO₂. Whereas back-reaction at the substrate is relatively unimportant under short circuit conditions, it must be taken into account at the maximum power point or at open circuit. The influence of the back-reaction on open circuit photovoltage decay measurements and on intensity modulated photovoltage (IMVS) measurements has been studied by model simulations and by experimental measurements. The simulations demonstrate that reliable information about DSC properties such as trapping distributions can only be derived from transient or periodic photovoltage responses if the back-reaction is suppressed by the use of suitable blocking layers.