ABSTRACT
Since its invention in 2004, graphene, a novel 2-dimensional (2D) material, has shown its uniqueness in exhibiting extraordinary properties. Graphene is a single layer of carbon atoms (C-C distance of 0.142 nm) with a hexagonal closed pack structure. It is an ultrathin, mechanically strong, transparent and flexible conducting material. The electrical conductivity of graphene is 1.4 times higher than that of Cu or Si (conductivity of graphene is ~80 × 106 Sm–1) and also has high thermal conductivity (Graphene: 3–5 KWm–1K–1, Cu: 400Wm–1K–1), making it the best thermal conductor [1]. Its conductivity can be increased over a large range either by changing the number of layers of graphene, also known as chemical doping, or by applying electric fields. Moreover, it also has high electron mobility (15,000 cm2/V.s) and a very large specific surface area (SSA ~ 2,630 m2/g) that render the material several interesting properties for various optoelectronic applications [2]. Further, graphene sheets are flexible as well as chemically inert, giving it a dual role: as an electrode and as a protective layer. However, some concerns associated with its high transparency (absorbs 2.3%), which is not favorable for solar cell applications, need to be resolved. This problem can be ideally solved by doping graphene to make p- to n-type. Together, these extraordinary properties of graphene make it an excellent candidate for energy harvesting devices such as solar cells as well as for sensors, photodetectors, etc.
