Edge-selectively antimony-doped graphene nanoplatelets as an outstanding cathode with an unusual electrochemical stability for dye-sensitized solar cells

Abstract

Despite of the advantages of dye-sensitized solar cell (DSSC), such as economic fabrication cost, transparency, full color, and high efficiency under weak light, it has been unsatisfied for practical use. To realize practical and/or large-scale commercial applications, developing low-cost, durable, and highly active electrocatalysts such as platinum (Pt) is one of the important issues. In this study, edge-selectively antimony-doped graphene nanoplatelets (SbGnPs) were prepared as an alternative candidate to substitute Pt electrodes by a simple environmental mechanochemical reaction between pristine graphite and Sb powder for counter electrode (CE) in dye-sensitized solar cells for the first time. The selective doping of Sb at the edges of graphene nanoplatelets (GnPs) and their structure were characterized by various analytical techniques including atomic-resolution transmission electron microscopy (AR-TEM). The prepared SbGnPs showed a lower charge-transfer resistance (Rct) compared to that of Pt as electrocatalysts toward to a Co(bpy)32+/3+ (bpy = 2,2＆rsquo;-bipyridine) redox couple, displaying ＆lsquo;zero loss stability＆rsquo; of electrocatalytic activity for the Co(bpy)33+ reduction reaction even after 1000 potential cycles. DSSCs with N-doped graphene nanoplatelet (NGnP) CE as a reference employing Co(bpy)32+/3+ were systematically evaluated as a comparison. The SbGnP-CE-based DSSC employing an SGT-021 sensitizer based on a D-＆pi;-A structured zinc(Ⅱ)-porphyrin showed better power conversion efficiency (12.08%) than the Pt (11.26%) or the NGnPs (11.53%). The superior electrocatalytic activity of the SbGnPs with and remarkable electrochemical stability suggests that they could be one of the best alternative to a Pt-CE for DSSCs in conjunction with cobalt electrolytes.