Impact of blocking layers based on TiO2 and ZnO prepared via direct current reactive magnetron sputtering on DSSC solar cells

Abstract

The optimization of dye-sensitized solar cells (DSSCs) technology towards suppressing charge recombination between the contact and the electron transport layer is a key factor in achieving high conversion efficiency and the successful commercialization of this type of product. An important aspect of the DSSC structure is the front blocking layer (BL): optimizing this component may increase the efficiency of photoelectron transfer from the dye to the semiconductor by reduction charge recombination at the TiO₂/electrolyte and FTO/electrolyte interfaces. In this paper, a series of blocking layer variants, based on TiO₂ and ZnO:TiO₂, were obtained using the reactive magnetron sputtering method. Material composition, structure and layer thickness were referred to each process parameters. Complete DSSCs with structure FTO/BL/m-TiO₂@N719/ EL-HSE/Pt/FTO were obtained on such bases. In the final results, verification of opto-electrical parameters of these cells were tested and used for the conclusions on the optimal blocking layer composition. As the conclusion, application of blocking layer consists of neat TiO₂ resulted in improvement of device efficiency. It should be noted that for TiO₂:ZnO/Cu_xO and TiO₂/Cu_xO cells, higher efficiencies were also achieved when pure TiO₂ was used as window layer. Additionally it was proven that the admixture of ZnO phase inspires V_oc and FF growth, but is overall unfavorable compared to pristine TiO₂ blocking layer and the reference cell, according to the final cell efficiency.