ZnO-nitrogen doped carbon derived from a zeolitic imidazolate framework as an efficient counter electrode in dye-sensitized solar cells

Abstract

By direct carbonization of ZIF-8 nanopowder under an inert atmosphere, ZnO-nitrogen doped carbon (ZnO-NC) materials have been prepared and added at different content values to polystyrenesulfonate-doped poly(3,4-ethylenedioxythiophene) (PEDOT:PSS) and employed as an efficient catalyst in dye-sensitized solar cells (DSSCs). The electrochemical analysis confirms that the prepared counter electrodes display catalytic activity higher than those of PEDOT:PSS and Pt CEs for I₃⁻/I⁻ and [Co(bpy)₃]^2+/3+ redox mediators. The photovoltaic conversion efficiency of the assembled DSSC with the 7% ZnO-NC/PEDOT:PSS catalyst and an I₃⁻/I⁻ based electrolyte is 8.05%. By increasing the thickness of the prepared counter electrode, the electrocatalytic activity is greatly enhanced and the total performance reaches 9.16%, which is 21.16% greater than that of the Pt-based cell (7.56%). Furthermore, ZnO-NC/PEDOT:PSS CEs are also confirmed to exhibit outstanding catalytic activity toward the [Co(bpy)₃]^2+/3+ redox couple. The resultant conversion efficiency of the assembled DSSC with a 7% ZnO-NC/PEDOT:PSS CE is 8.12%, which is greater than that of the Pt-based cell (7.49%).