Effect of Dip-Coating Cycles on the Structural and Performance of ZnO Thin Film-based DSSC

Deposition of thin film with good thickness uniformity and quality for fabrication of thin film-based dye-sensitized solar cells is a critical factor that determines the reliability and consistency of its photovoltaic performance. In this work, dip-coating method was used for the deposition of ZnO thin films on fluorine-doped tin oxide glass substrates. The structural, electrical and optical properties of these ZnO thin films were characterized by XRD, FESEM, four-point probe, UV–Vis spectroscope and room temperature PL spectroscope. The study showed that the thickness of ZnO thin film could be adjusted by the number of dipping cycles. By increasing the dip-coating cycles, the thickness, crystal quality and absorbance of visible light of ZnO thin films increased whereas the sheet resistance of ZnO thin films decreased. As a consequence, the photovoltaic performance of DSSCs improved with maximum conversion efficiency of 0.68% at 3 cycles of dip coating. Nevertheless, formation of macro-defects such as pores and cracks in thick ZnO thin films became the dominant factor that deteriorated their conversion efficiency down to 0.19% (at 11 cycles).