Investigating the effect of ZrO2 nanofibers in ZnO-based photoanodes to increase dye-sensitized solar cells (DSSC) efficiency: Inspecting the porosity and charge transfer properties in ZnO/ZrO2 nanocomposite photoanode

Abstract

This study is aimed to improve the performance of zinc oxide (ZnO) photoanodes in dye-sensitized solar cells (DSSCs) by exploiting the superior charge transport properties in electro-spun zirconium dioxide (ZrO2) nanofibers in ZnO/ZrO2 nanocomposite photoanodes. The fabricated photoanodes were analyzed by a variety of analyses. The XRD results show that photoanodes are a mixture of two different phases of ZnO and ZrO2 without any additional impurity phase. FESEM images and BET analysis show changes in porosity and effective surface area in the synthesized photoanodes. UV–Vis analysis confirms this conclusion by measuring adsorbed dye molecules on the photoanode surface. In addition, using the photoanodes, DSSCs are prepared for which J-V characterization results show an increase in efficiency from 1.68 to 3.31 %. The addition of ZrO2 nanofiber to the ZnO network increases the porosity and effective surface area and makes it possible to control the dye-loading as well as electrolyte species transport. Furthermore, the results of EIS analysis show that the charge transport in the ZnO/ZrO2 network is carried out more efficiently compared to the bare ZnO photoanode. Although, increasing ZrO2 nanofibers to a certain level can help improve the efficiency, it tends to reduce the efficiency with ZrO2/ZnO ratios of over 10 %.