ZnO-treated TiO_2 inverse opal electrodes for dye-sensitized solar cells

摘要

We report that the photovoltaic properties of inverse opal TiO_2 (io-TiO_2) electrodes in dye-sensitized solar cells can be enhanced by ZnO treatment of the inverse opal structures. ZnO was coated on the surface of io-TiO_2 via the sol-gel reaction of ZnO precursors. Energy dispersive X-ray spectroscopy (EDX) measurements showed that the amount of ZnO on the io-TiO_2 surface was measured to be 0.12-0.50 wt% of zinc, depending on the number of coatings. Compared to bare inverse opal electrodes, the energy conversion efficiency of cells increased for the 0.35 wt% ZnO-coated electrodes, and then decreased for the 0.50 wt% ZnO-coated electrodes. The maximum efficiency of 5.3% was achieved, corresponding to a 23% increase in efficiency compared with bare io-TiO_2 electrodes. The enhanced efficiency was mainly attributed to the improvement of the open-circuit voltage (V _(OC)). EIS and dark current measurements confirmed that this enhancement in V_(OC) was due to the movement of the conduction band edge in a negative direction after ZnO treatment, rather than the formation of a barrier layer for electron recombination.