Synthesis and Characterization of Graphene Oxide (GO) and Reduced Graphene Oxide (rGO) Thin Films as a Hole Transport Layer (HTL) on Azo-Kojic Compound for Organic Photovoltaic (OPV) Applications

Erdawaty, Mohd Jaafar (2019) Synthesis and Characterization of Graphene Oxide (GO) and Reduced Graphene Oxide (rGO) Thin Films as a Hole Transport Layer (HTL) on Azo-Kojic Compound for Organic Photovoltaic (OPV) Applications. Masters thesis, Universiti Malaysia Sarawak (UNIMAS).

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Abstract

Carbon-based nano-materials have undergone an explosion of interest, particularly Graphene Oxide (GO) and reduced Graphene Oxide (rGO). Both GO and rGO have appeared to be significant amidst all carbon-based materials with a wide range of applications. Hence, this research synthesized and characterized both optimized GO and rGO thin films by employing the improved and modified chemical vapour (hydrazine solution) methods to serve as a potential Hole Transport Layer (HTL) in Organic Photovoltaic (OPV) applications. GO is synthesized with varied parameters, including reaction time, degree of oxidation, and concentration of GO, while rGO is analyzed with various reduction temperatures and volumes of reduction agent. These parametric aspects are assessed to attain the optimization of both GO and rGO. Next, the optimized GO was deposited into thin films and is reduced to form rGO thin films. After that, a new compound called Azo Kojic (K-Azo) is developed. This compound is deposited on the surfaces of the optimized GO and rGO thin films. The effect of K-Azo compound on the GO and rGO surfaces is evaluated. Several characterization methods, such as Scanning Electron Microscope (SEM), X-ray Diffraction (XRD), Ultra-Violet Spectroscopy (UV-Vis), Fourier Transform Infra-red Spectroscopy (FTIR), Raman Spectroscopy, and I-V Characteristics, has been performed accordingly onto the GO and rGO samples. SEM images of the GO revealed crumple and wrinkled structure due to exfoliation of graphite with adequate reaction time and degree of oxidation (potassium permanganate, KMnO4), while the XRD pattern is identified as GO phase. The absorbance and vibrational information of GO was supported by UV-Vis and Raman Spectroscopy. The existing oxygen functional group seemed to be present in the GO samples, as determined via FTIR Spectroscopy. I-V characteristic showed improvement in electrical conductivity based to the parametric of GO. Meanwhile, the SEM images of rGO exhibited folded structure due to loss of oxygen functional groups with decent reduction in both temperatures and volumes of reduction agent (hydrazine solution), whereas the XRD pattern identified the rGO phase. The absorbance and vibrational information of rGO is verified by UV-Vis and Raman Spectroscopy, while the remaining oxygen functional group in rGO samples is determined via FTIR Spectroscopy. Finally, I-V characteristic displayed enhancement in electrical conductivity based to the parametric of rGO. In conclusion, GO is formed with 4.5 g of KMnO4 within 48 hours. In precise, the properties of GO appeared to be dependent on adequate reaction time and suitable degree of oxidation, while the properties of GO thin films are based on the concentration of GO solution, which is 8mg/ml. Reduction of GO thin films is achieved by altering the chemical method at 70 ˚C with 300 μl of hydrazine solution. This signified adequate reduction in both temperatures and volumes of reduction agent, which led to rGO thin films. In summation, the enhanced and modified chemical vapour a technique has been successfully developed rGO thin films from GO thin films. Finally, the presence of K-Azo compound enhanced the absorbance and electrical properties of both GO and rGO thin films which 4.07x10-7 S/cm and 1.10 x 10-3 S/cm.

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