Oxygen-assisted low-pressure chemical vapor deposition for the low-temperature direct growth of graphitic nanofibers on fluorine-doped tin oxide glass as a counter electrode for dye-sensitized solar cell

In this paper, we report an oxygen-assisted low-pressure chemical vapor deposition (LPCVD) method for the direct growth of graphitic nanofibers (GNFs) on a fluorine-doped tin oxide (FTO) glass substrate at a low temperature (550 degrees C). By adding moderate concentrations of oxygen in a gas mixture of argon, ethylene, and hydrogen during LPCVD, an extremely dense GNF forest can be obtained on a nickel-coated FTO glass substrate. Though this process, the graphitic nanofibers are grown homogenously on a large area of FTO glass. It was observed that oxygen-assisted LPCVD leads to the direct growth of high-quality GNFs as a counter electrode for dye-sensitized solar cells (DSSCs). In combination with an N719 dye-sensitized TiO2 working electrode and an iodine-based electrolyte, the DSSC with a GNF counter electrode showed a power conversion efficiency of 5.51% under AM 1.5 (100mWcm(-2)) illumination, which approached that of the DSSC with a Pt counter electrode (5.44%). The results demonstrated that our directly grown GNFs could be promising candidates for counter electrodes to achieve high performance in DSSCs. (C) 2014 The Japan Society of Applied Physics