Non-ohmic resistance effects of the AZO and TiZO as a blocking layer in dye-sensitized solar cells (DSSCs)

Abstract

Presented in this paper is the result of a study on the utilization of Al-doped ZnO (AZO) and Ti-doped ZnO (TiZO) as a blocking layer (BL) in Dye-Sensitized Solar Cells (DSSCs). The DSSCs structure was FTO/BL/TiO2/dye/electrolyte/Pt on FTO. The crystallinity and crystallite size of those BLs were shown to be affected by the dopant type and its concentration. From the photovoltaic characteristics of those DSSCs, the TiZO layer showed better contribution in enhancing the open voltage as a BL in comparison to the AZO. The effect of these layers on the solar cell characteristics in the fabricated DSSCs was found to be not merely due to the difference in their Ohmic resistance. There is also the contribution of back recombination kinetics from the photoexcited electrons via the dopant states in the AZO and TiZO layers, which are different among the layers due to the difference in dopant states distributions below their conduction bands.