Morphological and electron transport studies in ZnO dye-sensitized solar cells incorporating multi- and single-walled carbon nanotubes

Abstract

Dye-sensitized solar cells (DSSCs) incorporating zinc oxide (ZnO) nanostructures and carbon nanotubes (CNTs) were fabricated using a chemical bath deposition method. The nanoflake structures captured by a field-emission scanning electron microscopy analysis traced the appearance of multi-walled carbon nanotubes (MWCNTs) and single-walled carbon nanotubes (SWCNTs) in the photoanode thin film. The photovoltaic performance of the photoanode was quantified by means of an electrochemical impedance spectroscopy (EIS) unit with GAMRY-Physical Electrochemistry. The ZnO–SWCNT-based DSSC exhibited good photovoltaic performance with power conversion efficiency (η), photocurrent density (Jsc), open-circuit voltage (Voc) and fill factor (FF) of 1.31%, 15.31 mA cm−2, 0.224 V and 0.36, respectively. The EIS unit was also employed to quantify the charge transport resistance (Rct), transport resistance (Rt) and effective electron lifetime (τeff) of the DSSC. The impedance analysis of the ZnO–SWCNT-based DSSC also determined greater highly efficient electron transport due to long effective electron diffusion length than the film thickness of the photoanode.