Increasing the Photovoltaic Performance of Dye-Sensitized Solar Cells by Zinc Oxide Film as a Recombination Blocking Layer

Abstract

Dye-sensitized solar cells (DSSCs) have great potential in solar power generation due to their advantages of easy fabrication and low fabrication cost. One of the main problems of DSSCs is the loss of recombination between the fluorine-doped tin oxide (FTO) substrate/electrolyte. This is mainly due to the mesoporous nature of the TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> film. The recombination effect can be reduced by introducing compact layers (CLs) on the photosensitive layer to prevent the direct contact between the transparent conductive oxide substrate and the redox electrolyte. When compared with TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , zinc oxide (ZnO) tends to have more negative conduction band edges. This helps to prevent, electronic recombination reactions and so improves the open-circuit voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{{\text {OC}}}$ </tex-math></inline-formula> ). ZnO blocking layers (ZBLs) were deposited on the FTO substrate by RF sputtering and used for DSSCs. We employed a field emission scanning electron microscope (FE-SEM) and X-ray diffraction (XRD) to characterize ZBL. Photovoltaic (PV) parameters were measured on the DSSCs samples fabricated in this study under solar simulator illumination at AM 1.5 (100 mW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ). Compared with the DSSCs without ZBL, DSSCs with ZBL (31 nm) exhibit higher short-circuit current density ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${J}_{{\text {SC}}}$ </tex-math></inline-formula> ) and photovoltaic conversion efficiency (PCE), which is 21.82% higher than that of the DSSCs without ZBL.