Dye-Sensitized Solar Cells with Reduced Graphene Oxideas the Counter Electrode Prepared By a Greenphotothermal Reduction Process

Highly conductive reduced graphene oxide (rGO) with good electrocatalytic ability for reducing triiodide ions (I₃^-) is a promising catalyst for the counter electrode (CE) of dye-sensitized solar cells (DSSCs). However, hazardous chemical reducing agents or energy-consuming thermal treatments are required for preparing rGO from graphene oxide (GO). Therefore, it is necessary to find other effective and green reduction processes for the preparation of rGO and to fabricate rGO-based DSSCs. In this study, GO was prepared using a modified Hummers method from graphite powder, and further reduced to rGO through a photothermal reduction process (to give P-rGO). P-rGO shows better electrocatalytic ability due mainly to its high standard heterogeneous rate constant for I₃^- reduction and in part to its considerable electrochemical surface area. The corresponding DSSC shows a higher cell efficiency (η) of 7.62% than that of the cell with a GO-based CE (η= 0.03%). When the low-temperature photothermal reduction process is applied to all-flexible plastic DSSCs, the DSSC with a P-rGO CE shows an η of 4.16%.