Improved efficiency in front-side illuminated dye sensitized solar cells based on free-standing one-dimensional TiO_2 nanotube array electrodes

摘要

Although morphological disorder of nanotube structure is further down than the nanoparticular electrode, its density of traps are the hindering effects in the charge transport. In this study, crack-free TiO2 nanotube membranes, which obtained through a re-anodizing process, are fixed on transparent fluorine-tin-oxide glass by applying a few drops of Titanium Isopropoxide without needing the TiO2 powder paste. Front-side illuminated dye sensitized solar cells fabricated by undoped, N-doped and blue TiO2 nanotube membranes are investigated. The electrical characteristics of TiO2 nanotube based dye sensitized solar cells are followed by theoretical analysis using simple one-diode model. Morphology improvement is utilized to remove top irregular layers and the efficiency can be increased up to 56%. Annealing temperature, dopant, and tube orientation effects are examined on the cell efficiencies. The results show that elevating annealing temperature from 480 to 520 degrees C improve the cell efficiency up to 70%. Also, in the N-doped TiO2 nanotube membranes, improvement in efficiency is observed up to 40% as compared to undoped samples. Finally, different orientations of N-doped TiO2 nanotubes are studied and it is found that the through-hole morphology of N-doped TiO2 nanotube membrane shows noteworthy enhancement and an efficiency of about 8%.