Covalently functionalized graphene oxide with cobalt–nitrogen-enriched complex containing iodide ligand as charge carrier nanofiller for eco-friendly high performance ionic liquid-based dye-sensitized solar cell

Abstract

For the first time, a new class of heterocyclic conjugated cobalt complex with specially designed iodide ligand onto functionalized nitrogen-enriched graphene oxide sheets (Co-complex-NGO) was synthesized as efficient charge transferable nanofiller (NF), which promoted the photovoltaic performance of quasi-solid-state dye-sensitized solar cell (QS-DSSC). This NF is unique with active sites of heterocyclic Co-complex-NGO that can generate redox-active spices on the GO surface. The ionic liquid electrolyte consisted of highly dispersed hydrophilic Co-complex-NGO NF has more than 86% wider electrochemical window and a 64% lower charge transfer resistance compared to the bare ionic liquid-based electrolyte. Cells utilizing an optimized amount 0.75 wt% NFs indicated power conversion efficiency (η) of 7.287, showing 70.37% enhancement compared to the cells using a referenced electrolyte (4.277%). Such excellent η correlates with the induced formation of a π-π interaction-shielding model between aromatic systems in the electrolyte which effectively improves the open-circuit voltage and the short-circuit current density. Given the superior long-term stability of the optimized device and excellent photoelectric conversion efficiency of the promoted ionic liquid-based electrolyte, this research will open up a new way to overcome the drawbacks of volatile-liquid electrolytes.