Ultra-high thermoelectric performance in graphene incorporated Cu2Se: Role of mismatching phonon modes. (November 2018)

• Record Type: Journal Article
• Authors: Li, Meng; Cortie, David L.; Liu, Jixing; Yu, Dehong; Islam, Sheik Md. Kazi Nazrul; Zhao, Lanling; Mitchell, David R.G.; Mole, Richard A.; Cortie, Michael B.; Dou, Shixue; Wang, Xiaolin
• Is Part Of: Nano energy. Volume 53(2018)
• Page Start: 993
• Page End: 1002
• Publication Date: 2018-11
• Subjects: Thermoelectric -- Cu2Se/graphene nanocomposite -- Interfacial thermal resistance -- Density functional theory; Nanoscience -- Periodicals; Nanotechnology -- Periodicals; Nanostructured materials -- Periodicals; Power resources -- Technological innovations -- Periodicals; Nanoscience; Nanostructured materials; Nanotechnology; Power resources -- Technological innovations; Periodicals; 621.042
• DOI: 10.1016/j.nanoen.2018.09.041
• Languages: English
• ISSNs: 2211-2855

Abstract

Abstract: A thermoelectric material consisting of Cu2 Se incorporated with up to 0.45 wt% of graphene nanoplates is reported. The carbon-reinforced Cu2 Se exhibits an ultra-high thermoelectric figure-of-merit of zT = 2.44 ± 0.25 at 870 K. Microstructural characterization reveals dense, nanostructured grains of Cu2 Se with multilayer-graphene and graphite agglomerations located at grain boundaries. High temperature X-ray diffraction shows that the graphene incorporated Cu2 Se matrix retains a cubic structure and the composite microstructure is chemically stable. Based on the experimental structure, density functional theory was used to calculate the formation energy of carbon point defects and the associated phonon density of states. The isolated carbon inclusion is shown to have a high formation energy in Cu2 Se whereas graphene and graphite phases are enthalpically stable relative to the solid solution. Neutron spectroscopy proves that there is a frequency mismatch in the phonon density of states between the carbon honeycomb phases and cubic Cu2 Se. This provides a mechanism for the strong scattering of phonons at the composite interfaces, which significantly impedes the conduction of heat and enhances thermoelectric performance. Graphical abstract: fx1 Highlights: A synthesis method is reported for graphene-incorporated Cu2 Se nanocomposites. Nanoplate carbon inclusions strongly reduce the thermal conductivity. A record high thermoelectric figure-of-merit for Cu2 Se is achieved. Molecular dynamic simulations are carried out using density functional theory. The interfacial resistance is rationalized based on the diffusion mismatch model.