In solid state dye-sensitized solar cells (DSSCs), interfaces of solid electrolyte with both working and counter electrodes play particularly important roles in determining the overall energy conversion efficiency because processes such as photogeneration, separation and recombination of charges take place at the interfaces. For solid state DSSCs, in particular, it is expected that the charge transfer resistance at the solid polymer electrolyte/Pt counter electrode interface could also play an important role in determining the energy conversion efficiency in addition to the ionic conductivity of triiodide. The large charge transfer resistance is primarily due to the fact that the polymer electrolyte is less compatible with solid Pt counter electrode than liquid electrolyte. Therefore, the charge transfer resistance was attempted to be reduced by improving the compatibility between the solid polymer electrolyte and solid Pt counter electrode. For example, poly(ethylene glycol) (PEG) containing a thiol group at one side of the polymer chain (PEG-thiol) was used to modify the Pt counter electrode as a surface compatibilizer. DSSC using the modified Pt counter electrode with PEG-thiol yielded high cell performance of 4.1% at one sun conditions (cell size of 0.13 cm2) with the Voc= 0.60 V, Jsc=11.8 mA/cm2, and FF=0.58. Therefore, it is concluded that the reduction of the charge transfer resistance of solid-state DSSCs is also important in improving the efficiency in addition to the most widely blamed ionic conductivity for low efficiency.