Graphene Oxide Photoreduction Recovers Graphene Hot Electron Cooling Dynamics

Abstract

Reduced graphene oxide (rGO) is a bulk-processable quasi-amorphous 2D material with broad spectral coverage and fast electronic response. rGO sheets are suspended in a polymer matrix and sequentially photoreduced while measuring the evolving optical spectra and ultrafast electron relaxation dynamics. Photoreduced rGO yields optical absorption spectra that fit with the same Fano lineshape parameters as monolayer graphene. With increasing photoreduction time, rGO transient absorption kinetics accelerate monotonically, reaching an optimal point that matches the hot electron cooling in graphene. All stages of rGO ultrafast kinetics are simulated with a hot-electron cooling model mediated by disorder-assisted supercollisions. While the rGO room temperature 0.31 ps${}^{-1}$ electronic cooling rate matches monolayer graphene, subsequent photoreduction can rapidly increase the rate by ~10-12$\times$. Such accelerated supercollision rates imply a reduced mean-free scattering length caused by photoionized point-defects on the rGO sp${}^2$ sub-lattice. For visible range excitations of rGO, photoreduction shows three increasing spectral peaks that match graphene quantum dot (GQD) transitions, while a broad peak from oxygenated defect edge states shrinks. These three confined GQD states donate their hot carriers to the graphene sub-lattice with a 0.17 ps rise-time that accelerates with photoreduction. Collectively, many desirable photophysical properties of 2D graphene are replicated through selectively reducing rGO scaffolded within a 3D bulk polymeric network.

arXiv comment12 pages, 6 figures

References in corpus (26)

• The electronic properties of graphene
• Graphene Photonics and Optoelectronics
• Graphene photodetectors for high-speed optical communications
• Measurement of the Optical Conductivity of Graphene
• Graphene-Based Liquid Crystal Device
• Excitonic Effects on the Optical Response of Graphene and Bilayer Graphene
• Photo-excitation Cascade and Multiple Carrier Generation in Graphene
• Picosecond photoresponse in van der Waals heterostructures
• Dual-gated bilayer graphene hot electron bolometer
• Gate-activated photoresponse in a graphene p-n junction
• Photocurrent measurements of supercollision cooling in graphene
• Graphene oxide films for ultra-flat optics and linear and nonlinear integrated photonic circuits
• Disorder-Assisted Electron-Phonon Scattering and Cooling Pathways in Graphene
• Carrier dynamics in epitaxial graphene close to the Dirac point
• Ultrafast Relaxation Dynamics of Hot Optical Phonons in Graphene
• Supercollision cooling in undoped graphene
• Very Slow Cooling Dynamics of Photoexcited Carriers in Graphene Observed by Optical-Pump Terahertz-Probe Spectroscopy
• Observation of Intra- and Inter-band Transitions in the Optical Response of Graphene
• Hot carrier diffusion in graphene
• Charge versus energy transfer in atomically-thin graphene-transition metal dichalcogenide van der Waals heterostructures
• Ultra-sensitive and Wide Bandwidth Thermal Measurements of Graphene at Low Temperatures
• Ultrafast Carrier Recombination and Generation Rates for Plasmon Emission and Absorption in Graphene
• Transient absorption and photocurrent microscopy show hot electron supercollisions describe the rate-limiting relaxation step in graphene
• Direct observation of room temperature high-energy resonant excitonic effects in graphene
• Picosecond energy transfer in a transition metal dichalcogenide-graphene heterostructure revealed by transient Raman spectroscopy
• Ultrafast photocurrent and absorption microscopy of few-layer TMD devices isolate rate-limiting dynamics driving fast and efficient photoresponse