▎ 摘　　要

Graphene possesses exceptional mechanical, electrical, and thermal properties that stand out for numerous applications in materials and energy-related areas. The growing demand to produce high-quality large-scale graphene films inexpensively remains a challenge. The work presented in this paper emphasizes a straightforward method of producing high-quality graphene films using cellulose as the starting materials. We demonstrate the synthesis of defect-free graphene films (as thin as similar to 10 layers) on substrates up to 7 cm(2) in area. Graphitic films were characterized using Infrared Raman, energy-dispersive X-ray spectroscopy, X-ray diffraction (XRD), scanning electron microcopy SEM, and high-resolution transmission electron microscopy (HRTEM). Our XRD, Raman, and HRTEM studies indicated that the synthetic temperature was critical in the synthesis of high-quality graphene films using cellulose as the carbon source material. Systematic studies revealed that defect-free large area graphitic films were produced at a synthetic temperature of similar to 900 degrees C. The Raman D band peak intensity decreased for the samples synthesized at higher temperature but was absent for the samples prepared at 900 degrees C. Both the HRTEM and selected area electron diffraction confirm the highly ordered arrangement of carbon atoms in the sample matrix. The measured distance between lattice fringes was 0.335 nm, which matches with the literature reported fringe distance for the high-quality graphene. The XRD spectrum of the thin graphitic samples synthesized at 900 degrees C displayed a sharp diffraction peak 28-26.5 degrees characteristic of highly crystalline defect-free graphene. Functional photodetector and photovoltaic (PV) devices were fabricated using graphitic films. The graphitic films were used as one of the electrodes for the PV devices yielded a power conversion efficiency of similar to 1%. Our synthetic method can be potentially used for producing high-quality free-standing graphene films inexpensively at large-scale.