Three-dimensional ordered macroporous carbon as counter electrodes in dye-sensitized solar cells

Three-dimensional ordered macroporous carbon (3DOM-C) was synthesized through polystyrene (PS) colloidal crystal templates using carbonized glucose solutions as a carbon source and sulfuric acid as a dehydrating agent. The obtained samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen-sorption isotherm measurement. SEM results showed that the layers of the PS templates were hexagonal close-packed with a large surface area, and the diameter of the PS microspheres was 300–320   nm. SEM and TEM results demonstrated that the 3DOM-C displayed a unique structure of a well-developed 3D-interconnected ordered macroporous framework with a pore diameter of 260–280   nm. The photovoltaic current voltage curves showed that the dye sensitized solar cells (DSSC) fabricated by the 3DOM-C as a counter electrode exhibited an energy conversion efficiency ( η   =   2.91%), a short circuit current ( J sc   =   9.51   mA/cm 2 ), an open circuit voltage ( V oc   =   0.59   V) with a fill factor ( FF   =   52%), which were much closed to those of Pt counter electrode-based DSSC (3.59%, 10.05   mA/cm 2 , 0.59   V, 58%) and better than those of activated carbon-based one. Moreover, the electrochemical impedance spectroscopy analysis demonstrated a low charge-transfer resistance ( R CT ) for 3DOM-C (3.48 Ω cm 2 ), which was close to that of Pt (1.54 Ω cm 2 ), and much lower than that of activated carbon (15.05 Ω cm 2 ). Finally, the 3DOM-C showed a comparable efficiency compared to a conventional Pt counter electrode.