Electron recombinations in electrolyte solution reduce light-to-energy conversion efficiency at the nanoporous electrode surface of dye sensitized solar cells. In this study, we improved the conversion efficiency using an energy barrier at the nanoporous electrode surface to control the recombination process. The energy barrier was formed by coating nanoporous TiO2 electrode with Nb2O5 material. We investigated the influence of energy barrier on the cell efficiency depending on the coating thickness. Nanoporous TiO2 electrode was coated about 5 nm thickness by 12 times coatings, and so the coating layer was grown about 0.417 nm for every time. Enhancement of conversion efficiency from 2.55% to 4.25% was achieved at 0.834 nm coating thickness, and it was believed as the optimum thickness for minimizing the electron recombination process in our experimental system.