Transparency and Diffused Light Efficiency of Dye-Sensitized Solar Cells: Tuning and a New Figure of Merit

Abstract

Tunability is considered one of the main advantages of dye-sensitized solar cells (DSSCs) over conventional Si-based solar cells. In DSSCs, the thickness of the active layer can tune the transparency of the cell. This, however, creates a tradeoff between the transparency and the cell's efficiency. DSSCs with tailored transparency would be capable of being utilized in photovoltaic window applications, where Si cells are barely suitable. In this article, a new figure of merit is introduced to evaluate the performance of the DSSCs, named “TED efficiency.” The proposed TED parameter (i.e., the transparency, conversion efficiency, and diffused light efficiency) not only is based on the cell conversion efficiency but also considers the optical transparency as well as the cell performance under diffused light. TED efficiency measurements were performed on three different types of DSSCs: standard (DSSC-A), simple semitransparent (DSSC-B), and scattering-enhanced DSSCs (DSSC-C). A 22.5%-transparent DSSC has been fabricated by reducing the thickness of the porous TiO2 layer. To optimize the TED efficiency of the semitransparent DSSC, an opaline SiO2 layer is used. This layer enhances the forward scattering, acts as an UV protecting layer, and colorizes the semitransparent cell in a decorative manner. The TED efficiency for the scattering-enhanced DSSC showed a significant improvement to the standard DSSC as well as to the semitransparent cell.