Graphene, a one-atomic carbon sheet with a honeycomb structure, has attracted significant attention due to its unique physical properties. This material shows an extraordinarily high carrier mobility and is considered to be a major candidate for future high speed transistor materials. One of the many interesting properties of Dirac electrons in graphene is the drastic change of conductivity of the graphene-based structure within the confinement of electrons. Structures based on graphene that realize this behavior are carbon nanotubes and graphene nanoribbons with periodic and zero boundary conditions, respectively, for the transverse electron wave-vector. The limited control over the chirality and diameter of nanotubes, and thus of the associated electronic band gap, remains a major technological problem. Recently, graphene sheets have been patterned into narrow nanoribbons. Graphene nanoribbons have recently attracted much interest as they are recognized as promising building blocks for nanoelectronic devices. The electronic properties of such ribbons exhibit a dependence on their direction and width. The band gap of semiconducting Graphene NanoRibbon (GNR) Devices is inversely proportional to their width. By modulating the width of a GNR in real space, heterojunctions can be achieved. Moreover, owing to excellent optical properties, an all graphene nanoribbon electronic and opto-electronic circuit can be envisioned. The direct band gap and the tunability of the band gap with the ribbons' width, renders the ribbons as suitable candidates for opto-electronic devices, especially for infra-red applications due to the relatively narrow band gap. To explore the physics of such devices, self-consistent quantum mechanical simulations have been performed. The performance of infra-red photo detectors based on graphene nanoribbons is analyzed numerically by employing the Non-Equilibrium Green's Function (NEGF) formalism. This method has been successfully utilized to investigate the characteristics of carbon nanotube devices. To extend our previous work, we employ the NEGF method based on the tight-binding model to study electronic and optoelectronic properties of graphene nanoribbons, and also to investigate methods to improve the performance of such devices.