Indium-tin-oxide-based transparent conducting layers for highly efficient photovoltaic devices

Additional hydrogen (H₂) annealing and subsequent electrochemical treatment are found to make tin-doped indium oxide (ITO)-based photoelectrodes suitable for highly efficient dye sensitized solar cells. The additional H₂ annealing process recovered the electrical conductivity of the ITO film the same as its initial high conductivity, which enhanced the charge collecting property. Moreover, the employment of electrochemical oxidation of TiO₂/ITO photoelectrode improved the energy conversion efficiency of the ITO-based dyesensitized solar cells (DSSC), higher than that of a conventional FTO-based DSSC. Electrochemical impedance analysis showed that the H₂ annealing process reduced the internal resistance of the cell, i.e., the resistance of the ITO and the Schottky barrier at the TiO ₂/ITO interface were reduced, and that the electrochemical treatment recovered the diodelike characteristics of the DSSC by retarding back electron transfer from the photoelectrode to the electrolyte. The present work demonstrates that thermally and electrochemically modified ITO-based photoelectrode is another alternative to the conventionally used FTO-based photoelectrode.