Reduced Graphite Oxide-Indium Tin Oxide Hybrid Materials for use as a Transparent Electrode

Abstract

Reduced graphite oxide (rGO)-indium tin oxide (ITO) hybrid materials suitable for spin-coating transparent electrodes were synthesized and evaluated. GO was made using a modified Hummers method and was reduced by p-phenylene diamine (PPD-rGO) or hydrazine hydrate (HYD-rGO). Raman spectra showed that the G-band of PPD-rGO or HYD-rGO down-shifted from 1599 to 1583 cm−1 and the intensity ratio of the D-band with respect to the G-band increased from 0.67 to 0.91 or 0.83, indicating the recovery of the hexagonal network of carbon atoms with defects. According to elemental analysis data, oxygen content decreased from 44.34 to 19.58 and 18.30 after GO was treated by PPD or HYD. After adding 0.66 wt % PPD-rGO or HYD-rGO into sol-gel ITO, the sheet resistance of the film decreased from 2 × 103 to 1.0 × 103 or 0.7 × 103 Ω/sq, respectively. Further, transmittances as high as 87% were maintained. The operating voltage at 30 mA/cm2 in organic light emitting diodes using hybrid materials of HYD-rGO and ITO as anodes decreased from 23.8 to 14.2 V. Luminance at 90 mA/cm2 increased from 7500 to 11000 cd/m2. Therefore, rGO effectively reduces the sheet resistance of sol-gel ITO.