New counter electrode of hot filament chemical vapor deposited graphene thin film for dye sensitized solar cell

The hot filament chemical vapor deposition (HFCVD) was employed for the direct growth of graphene like thin film on fluorine doped tin oxide (FTO) glass substrates without using any catalyst. The key parameters like carbon precursors such as CH4 and C2H2 gases and the filament temperatures were optimized to achieve the uniform graphene like thin film on FTO glass substrates through the HFCVD deposition technique. The optimized parameters of CH4 (1 sccm), deposition time (5 min) and the filament temperature of 1400 °C produced the uniform graphene like thin film on FTO glass substrates whereas, the diamond like carbon on FTO glass substrates was achieved with C2H2 precursor gas. The appearance of significant G and small 2D peaks in the Raman spectra confirmed the deposition of graphene like thin film by using CH4 as precursor gas. The existence of surface chemical species or functional groups on the deposited graphene like thin film were deduced by the X-rays photoelectron spectroscopy (XPS), which indicated the good quality graphene like thin film on FTO glass substrate through HFCVD technique. The HFCVD grown graphene like thin films were applied as counter electrode for the fabrication of dye sensitized solar cell (DSSCs) and showed considerably high electrocatalytic activity towards the reduction of I3- ions in the redox electrolyte. The relatively high solar to electrical conversion efficiency of ∼4.3% with the short-circuit current density (JSC) of ∼8.65 mA/cm2, open circuit voltage (VOC) of ∼0.728 V with high fill factor (FF) of ∼0.68 were achieved by DSSC fabricated with graphene like thin film electrode obtained from CH4 as precursor gas.

► Direct and catalyst free growth of graphene like thin film on FTO by HFCVD method.
► Uniform graphene like thin film on FTO glass is obtained with CH4 with filament temperature of 1400 °C.
► Graphene thin film electrode shows considerably high electrocatalytic activity.
► DSSC fabricated with graphene counter electrode achieves high conversion efficiency of ∼4.3%.
► HFCVD technique grows the good quality graphene like thin film on the FTO glass.