The combined effect of brookite TiO₂ and magnetron-sputtered ITO film on the performance of dye-sensitized solar cells

Introduction

The advancement of nanoscience and technology has brought new insight into the field of DSSCs (dye-sensitized solar cells). In this work, DSSCs werefabricated on top of an ITO (indium-doped tin oxide) film deposited by magnetron sputtering in the presence of monolithic inert gas. Further, the use of brookite TiO₂ as a photoanode proved to have a significant influence on enhancing efficiency compared to the standard device.

Methods

The ITO layers were manufactured in the radio frequency (RF) magnetron sputtering system following our recent report at a pressure set point of 5 × 10⁻³ mbar, with an RF power of 70 W, rotation speed of 20 a.u., and Ar flow of 20 sccm. After the film deposition, it was annealed at 500 °C for 2 h in a nitrogen atmosphere. The brookite TiO₂ was synthesized following our previous report, and a paste was prepared using ethyl cellulose, terpineol, and ethanol. The paste was coated by doctor blading and annealed at 400 °C, followed by cooling. For a sandwich-type device fabrication, N719 dye, iodide-tri-iodide electrolyte, and a Pt top electrode were used.

Results

The 150 nm coated ITO film gave a nice balance of sheet resistance and transmittance of ~10 Ohm/square and ~80%, respectively. The champion device with sputtering-deposited ITO and brookite TiO₂ produced a power conversion efficiency (PCE) of 7.7%, which is 28% higher compared to a commercial TiO₂/ITO glass-based champion device. The photovoltaic outcome was further verified using external quantum efficiency and impedance spectroscopy measurements.

Conclusions

The introduction of laboratory-developed ITO and combination with synthesized brookite TiO₂ shows a new approach to enhancing the efficiency of DSSCs. The importance of quality thin-film deposition by RF magnetron and the importance of the variable crystal structure of TiO₂ or other semiconducting materials for photovoltaic devices are demonstrated.