Enhanced performance of dye-sensitized solar cell with thermally-treated TiN in its TiO_2 film prepared at low temperature

摘要

Various weight percentages of titanium nitride (TiN) and thermally-treated titanium nitride (tt-TiN) are incorporated into the binder-free TiO_2 films, prepared at low temperature (LT, 120℃), and the corresponding dye-sensitized solar cells (DSSCs) are made. Effects of their incorporation on the photovoltaics of the DSSCs are studied. With the incorporation of 0.125 wt% of TiN in a TiO_2 film of only 5.5 μm-thickness, the corresponding solar-to-electricity conversion efficiency (η) has reached to 3.40% from 2.38% of a cell with a bare TiO_2 film of same thickness; this increase in efficiency is attributed to the higher electron conductivity and longer electron life time in the TiO_2 film with TiN. Incorporation of 1.0 wt% of tt-TiN into the TiO_2 film has further improved the conversion efficiency to 3.77%; this further enhancement in the efficiency is attributed to the partial conversion of TiN into TiO_2 due to the thermal treatment (450℃). X-ray diffraction (XRD) and scanning electron microscopy (SEM) are used to study the partial conversion of TiN into TiO_2. Other explanations are supported by the data of UV-absorption spectra, electrochemical impedance spectroscopy (EIS), and laser-induced photo-voltage transients.