A novel low-cost method for fabricating high-performance plasmonic graphene for use in thin-film photovoltaic devices and other optoelectronics.
Plasmonic graphene, the combination of graphene with noble-metal nanostructures, promises the versatility of graphene with the ability to endow devices working in different frequency ranges with high speed, low power consumption and compact sizes. The benefits of plasmonic graphene are particularly promising in the pursuit of increasing light absorption in thin-film photovoltaic devices. KU faculty have developed a novel low-cost method for fabricating high-performance plasmonic graphene for use in thin-film photovoltaic and other optoelectronic devices.
Alternative to indium tin oxide (ITO) as transparent conductors in photovoltaics.
The three major steps in this method include:
1) Cleaning the surface of the chemical vapor deposition (CVD) graphene before deposition of metal films so a lean interface between metal and graphene can be formed.
2) Deposition of the metal films on graphene using suitable candidates.
3) Thermal treatment of the metal/graphene assembly to generate metal nanoparticles (NPs).
This KU lab fabricated plasmonic graphene using thermally assisted self-assembly of silver nanoparticles on graphene. The localized-surface-plasmonic effect is demonstrated with the resonance frequency shifting from 446 nm to 495 nm when the lateral dimension of the Ag nanoparticles increases from about 50 nm to 150 nm. Finite-Difference Time-Domain simulation was employed to confirm the experimentally observed light scattering enhancement in the plasmonic graphene and the decrease of both the plasmonic resonance frequency and amplitude with increasing graphene thickness. In addition, the experimental plasmonic graphene shows much-improved electrical conductance by a factor of 2-4x as compared to the original graphene, making the plasmonic graphene a promising advanced transparent conductor with enhanced light scattering for thin-film optoelectronic devices.
ITO is widely used as a transparent conductive electrode but has severe limitations. It is scarce and, therefore, becoming more and more expensive as demand for photovoltaic devices rises. In addition, ITO is brittle and has dramatically reduced transparency at longer wavelengths - unfavorable traits for high-efficiency, broadband photovoltaic devices on flexible substrates. Graphene has several unique advantages over ITO as the TC for photovoltaic devices: high electrical conductivity, remarkable optical transparency, and favorable work function of ~4.42 eV. Recent discoveries in large-area growth of graphene using chemical vapor deposition (CVD) on metal foils have made this high-performance material cost effective as well.
Low cost manufacture of a variety of electronic and optoelectronic devices.