Graphene-based Nanocomposites for Electro-optic Devices

Graphene, the most exciting carbon allotrope, and its derivatives such as graphene oxide and graphene quantum dots have sparked a flurry of research and innovation owing to their unprecedented optoelectronic properties. Graphene and its nanocomposites have been widely used in a variety of opto-electronic devices such as photodetectors, transistors, actuators, biomedical aids, and membranes. Their sp2 hybridization state provides some extraordinary opto-electronic and mechanical properties. Chemical exfoliation of graphite into graphene and graphene oxide allows us to mix graphene nanocomposites into various layers of organic solar cells and other organic semiconductor-based optoelectronic devices, especially for roll-to-roll fabrication of large-area devices at a lower cost. Recently, these nanocomposites have also been utilized as charge transport layers and surface modifiers in perovskite solar cells and perovskite light-emitting diodes. Researchers have found that the presence of graphene, even at very low loading, can significantly improve the device's performance. In this chapter, we have discussed the application of graphene oxide, reduced graphene oxide, and doped graphene oxide in various combinations in perovskite solar cells and perovskite light-emitting diodes; these nanomaterials can be utilized either in transport layers of a multilayered device or directly incorporated in the active layers of these optoelectronic devices. These nanocomposites generally improve the device efficiencies by improving the band alignment at heterojunctions in a multilayered device by substantially reducing the trap states and the charge transfer resistance. These nanocomposites are found to achieve significantly improved device power conversion efficiency and stability of perovskite-based optoelectronic devices.

Keywords: Band alignment, Graphene-oxide, Hybridization, Low cost, Nanocomposites, Opto-electronic, Perovskite optoelectronic devices, Power-conversion efficiency, Stability, Trap-states