Farklı grafen esaslı malzemelerin hazırlanması ve karakterizasyonu ve grafen/silisyum schottky eklemli güneş hücresinin incelenmesi

In this thesis, three graphene forms are synthesized using practical and cost-effective methods. Graphene oxide (GO) powder, few-layer graphene flakes (FLG), and monolayer graphene sheet have been synthesized by modified Hummers' method, electrochemical exfoliation (EE) method, and chemical vapor deposition method (CVD), respectively. Pure GO with lateral size of 4-80 μm was successfully synthesized. High-quality FLG were synthesized by EE method followed by sonication in DMF and rapid microwave (MW) treatment. Raman spectra confirms the formation of few-layer graphene in the final product. High quality mono-layer graphene sheet was on the copper foil was confirmed by Raman Spectroscopy measurements with I2D/IG = 2.05 and low defect density of ID/IG = 0.14. Graphene based photovoltaic device has been investigated, where CVD graphene sheet with n-type silicon in order to fabricate graphene/silicon (G/Si) Schottky junction solar cell with top-window structure and active area of 0.11 cm2. The effect of moderate and high-doped n-Si were investigated for making Schottky device. The effect of etching time of SiO2, thermal annealing to graphene, and p-doping graphene were also examined. Annealing treatment showed a noteworthy reduction in the PMMA residue, while, graphene p-doping with nitric acid vapors and GO dispersion showed an enhancement in graphene's work function. The best obtained power conversion efficiency (PCE) was found around 3.2% in Pristine graphene/moderate n-Si, and 2.24% in p-G/highly n-Si Schottky junction solar cell after thermal annealing and doping with synthesized GO.