Modifying TiO₂ surface architecture by oxygen plasma to increase dye sensitized solar cell efficiency

Oxygen plasma treatment of TiO₂ films has been used to improve the efficiency of dye sensitized solar cells.Both a commercial TiO₂ sample and a TiO₂ thin film synthesized by a sol-gel technique were treated using a custom built inductively coupled plasma apparatus.X-ray photoelectron spectroscopy revealed that oxygen-plasma treatment increased the number of oxygen functional groups (hydroxyl groups) and introduced some Ti ^{3 +} species on the surface of TiO₂.A sample solar cell with plasma treated TiO₂ showed an overall solar-to-electricity conversion efficiency of 4.3%, about a 13% increase over untreated TiO ₂.The photon conversion efficiency for the plasma treated TiO ₂ was 34% higher than untreated TiO₂.This enhanced cell-performance is partly due to increased dye adsorption from an increase in surface oxygen functional groups and also may be partly due to Ti^{3 +} states on the surface of TiO₂.