Effects of Surface-modified Photoelectrode on the Power Conversion Efficiency of Dye-Sensitized Solar Cells

The effects of Na2SO4 as a surface modification material on the performance of dye-sensitized solar cells (DSSCs) were studied. The surfaces of TiO2 films were firstly modified with aqueous Na2SO4 solution by a dip coating process, and then the resulting electrode was applied to the photoelectrode of a DSSC. The DSSC with the Na2SO4-modified photoelectrode had a power conversion efficiency of 9.01% compared with that (7.97%) of the reference cell, which corresponds to an increase of about 13.0% in the efficiency due to an enhancement in short-circuit current (J(sc)) and open-circuit voltage (V-oc). A series of measurements such as UV-visible absorption, electrochemical impedance, incident photon to current conversion (IPCE) efficiency and dark current revealed that incorporation of Na2SO4 onto the TiO2 film led to an increase of dye adsorption and a longer lifetime of electrons injected from dyes to the TiO2 electrodes, resulting in the improvement in both J(sc) and V-oc, compared to those of a reference device without surface modification.