TECHNOLOGY FOCUS - POLYMERS - Preferred Method: In manufacturing graphene, the metal thin film comprises at least one metal selected from nickel (Ni), cobalt (Co), iron (Fe), platinum (Pt), gold (Au), aluminum (Al), chromium (Cr), copper (Cu), magnesium (Mg), manganese (Mn), molybdenum (Mo), rhodium (Rh), silicon (Si), tantalum (Ta), titanium (Ti), tungsten (W), uranium (U), vanadium (V), zirconium (Zr), zinc (Zn), strontium (Sr), yttrium (Y), niobium (Nb), technetium (Tc), ruthenium (Ru), palladium (Pd), silver (Ag), cadmium (Cd), indium (In), rhenium (Re), osmium (Os), iridium (lr) and lead (Pb). The carbon source material is a vapor, a liquid, or has a solid phase, or combination. The carbon source material is a vapor, and the heating (d) is performed in a range of 300-1400 degrees C and maintained for 10 seconds to 24 hours at a speed of 0.1-500 degrees C/second. The method further comprises forming a graphene sheet using the graphene prepared from the step (f). The metal thin film has a thickness of 1 nm to 10 mu m. The step (b) comprises forming a metal thin film on the subject substrate and heat-treating the subject substrate to naturally form a pattern. Alternatively, manufacturing graphene comprises: (a) preparing a subject substrate; (b) forming a metal thin film on the subject substrate and heat-treating the metal thin film to increase the grain size of the metal thin film; (c) heating the subject substrate and the metal thin film; (d) supplying a carbon source material on the heated metal thin film; (e) diffusing carbon atoms generated from the supplied carbon source material due to thermal decomposition into the metal thin film; and (f) forming graphene on the subject substrate by the carbon atoms diffused through the metal thin film. The heating (c) is performed in a temperature of 400-1200 degrees C maintained for 10 seconds to 24 hours at a speed ranging from 0.1-300 degrees C/sec. The method further comprises forming the graphene prepared in the step (f) into a graphene sheet. Preferred Display: The display comprises a liquid crystal display, an electronic paper display, or an optoelectronic device. Preferred Device: The electronic device is a transistor, a sensor, or an organic/inorganic semiconductor device. In the optoelectronic device, the organic optoelectronic device comprises an electron injection layer (EIL) and a hole injection layer (HIL). Preferred Solar Cell: Alternatively, the solar cell comprises lower and upper electrode layers laminated on a substrate and at least one active layer between the lower and upper electrode layers, where the active layer is the active layer. EXAMPLE - No suitable example given.