Plasma processed carbon thin films applied to dye-sensitized solar cells

Plasma-treated carbon thin films are investigated as counter electrodes for dye-sensitized solar cells. The films were grown onto fluorine-doped tin oxide (FTO) substrates by magnetron sputtering using pure graphite target and argon atmosphere and subsequently annealed at 600 °C for 30 min in vacuum. These films were then submitted to a plasma texturing process in a reactive ion etching reactor using three different gas combinations: sulfur hexafluoride/argon (SF 6 + Ar), sulfur hexafluoride/hydrogen (SF 6 + H 2 ), and sulfur hexafluoride/oxygen (SF 6 + O 2 ). The morphology and structure of the obtained films were characterized by scanning electron microscopy and Raman spectroscopy. Cyclic voltammetry technique allowed accessing the improvements in their catalytic properties, while the photocurrent-voltage curves under simulated solar illumination AM 1.5G (100 mW/cm 2 ) evaluated the performance of the respective assembled solar cells. The results show that photovoltaic performance is significantly affected by the different plasma texturing conditions used. The carbon counter electrode obtained after SF 6 + O 2 plasma texturing achieved the best power conversion efficiency of 2.23%, which is comparable to the 2.31% obtained using the commercial platinum counter electrode. Graphical abstract Reactive Ion Etching reactor for plasma texturing process of carbon thin films