On purpose to prepare solid-state dye-sensitized solar cells (DSSCs) with high energy-conversion efficiency, poly(ethylene glycol) (PEG) oligomer having specially designed terminal groups was used as the electrolyte for DSSCs. PEG oligomers exhibit good ionic diffusivity, negligible vapor pressure at room temperature and great thermal and long-term stability. Accordingly, they can be employed as alternatives to common volatile electrolytes for DSSCs. In spite of these advantages, however there have been few applications of oligomers to DSSCs since PEG oligomers are still liquid-state not solid-state. To solve this problem, we introduced novel oligomers which could be easily solidified via secondary interaction. Compared with the oligomers having secondary interaction sites and other oligmers with similar molecular weight to the totally interacted oligomers but not containing interaction groups, the ionic diffusion coefficients of I^- and I₃^- in the former were much higher than those for the latter. As a result of the J-V measurement, the DSSCs using the oligomer showed high energy-conversion efficiency over 4.5% and finally, a further test involving storage at room temperature demonstrated that the DSSCs employing the oligomer electrolytes showed superior stability to those of employing volatile electrolytes.