title: Surface morphology changes of graphene on flexible PET substrate upon thermal annealing.
abstract: The performance of a polymer photovoltaic device using multilayered graphene on an amorphous PET substrate as the electrode was studied. The changes in surface morphology of graphene coated polyethylene terephthalate (PETG) substrate upon thermal annealing were investigated by atomic force microscopy (AFM), field emission scanning electron microscope (FE-SEM) and current-voltage characteristics. The root mean square (RMS) roughness of PETG substrate before annealing was 36.5 nm that decreased to 11.5 nm after 10 min thermal annealing at 110 degrees C. The mean grain size of the substrate decreased from 2301 nm2 to 848 nm2. The PETG surface became smooth when thermally annealed as the voids created by the bubbles in the graphene layer were filled up with thermal expansion of the PET substrate. However, cracks present initially on the graphene due to surface stress between the graphene and PET layer grew further upon annealing that deteriorated the device performance. This study on the graphene surface morphology change upon annealing and the consequent drop in device performance vis-à-vis an ITO glass electrode shows potential drawback of solar cell device fabrication on such flexible substrates.
authors.affiliation: Division of Bionanotechnology, Gachon Bionano Institute, Kyungwon University, Seongnam, 461-701, Korea.
authors.forename: Monica
authors.initials: M
authors.lastname: Samal
authors.forename: Jong Min
authors.initials: JM
authors.lastname: Lee
authors.forename: Won Il
authors.initials: WI
authors.lastname: Park
authors.forename: Dong Kee
authors.initials: DK
authors.lastname: Yi
authors.forename: Ungyu
authors.initials: U
authors.lastname: Paik
authors.forename: Chang-Lyoul
authors.initials: CL
authors.lastname: Lee
mesh_terms: D004566:Electrodes; D006108:Graphite / Q000737:chemistry*; D036103:Nanotechnology / Q000379:methods*; D010777:Photochemistry; D018583:Pliability; D011093:Polyethylene Terephthalates / Q000737:chemistry*; D013059:Spectrum Analysis, Raman; D013499:Surface Properties
chemical_list: D011093:Polyethylene Terephthalates; D006108:Graphite