Exciton dynamics at molecule-metal interfaces:<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mi mathvariant="normal">C</mml:mi><mml:mn>60</mml:mn></mml:msub><mml:mo>∕</mml:mo><mml:mi mathvariant="normal">Au</mml:mi><mml:mrow><mml:mo>(</mml:mo><mml:mn>111</mml:mn><mml:mo>)</mml:mo></mml:mrow></mml:mrow></mml:math>

Dutton, Gregory; Quinn, Daniel P.; Lindstrom, C. D.; Zhu, Xiaoyang

doi:10.1103/physrevb.72.045441

Cited by 59 publications

(62 citation statements)

References 49 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Energetic ordering of the states was determined by changing the wavelength of the probe pulse and measuring the change in photoelectron energy. The increased binding of the n=1 image potential state at the 6T/Ag(111) interface compared to the clean silver binding energy of -.77 eV is consistent with other organic semiconductor metal interfaces that have a high electron affinity (> 2 eV) 30,63,64 . Increased coverage had a negligible affect on the workfunction or binding energy of the n=1 peak.…”

Section: Resultssupporting

confidence: 52%

Watching Electrons Transfer from Metals to Insulators using Two Photon Photoemission

Johns

2010

View full text Add to dashboard Cite

Ultrafast angle-resolved two photon photoemission was used to study the dynamics and interfacial band structure of ultrathin films adsorbed onto Ag(111). Studies focused on the image potential state (IPS) in each system as a probe for measuring changes in electronic behavior in differing environments.The energetics and dynamics of the IPS at the toluene/Ag(111) interface are strongly dependent upon coverage. For a single monolayer, the first IPS is bound by 0.81 eV below the vacuum level and has a lifetime of 50 femtoseconds (fs). Further adsorption of toluene creates islands of toluene with an exposed wetting layer underneath. The IPS is then split into two peaks, one corresponding to the islands and one corresponding to the monolayer. The wetting layer IPS shows the same dynamics as the monolayer, while the lifetime of the islands increases exponentially with increasing thickness. Furthermore, the island IPS transitions from delocalized to localized within 500 fs, and electrons with larger parallel momenta decay much faster. Attempts were made using a stochastic model to extract the rates of localization and intraband cooling at differing momenta.In sexithiophene (6T) and dihexyl-sexithiophene (DH6T), the IPS was used as a probe to see if the nuclear motion of spectating side chains can interfere with molecular conduction. The energy and band mass of the IPS was measured for 6T and two geometries of DH6T on Ag(111). Electrons injected into the thicker coverages of DH6T grew exponentially heavier until they were completely localized by 230 fs, while those injected into 6T remained nearly free electron like. Based off of lifetime arguments and the density of defects, the most likely cause for the mass enhancement of the IPS in this system is small polaron formation caused by coupling of the electron to vibrations of the alkyl substituents. The energetic relaxation of the molecular adsorbate was also measured to be 20 meV/100 fs for the DH6T, and 0 meV/100 fs for the 6T. This relaxation is consistent with the localization of the charge creating a barrier for it moving from one lattice site to a neighboring one.Finally, the IPS was used to study the evolution of the surface band gap at the Mg/Ag(111) interface. The Mg(0001) surface band gap lies 1.6 eV below the Fermi level, and consequently shows no peak in the projected density of states for the IPS. A method for creating layer by layer growth of Mg on Ag(111) was determined using Auger Spectroscopy and low energy electron diffraction. By monitoring the decay of the 1 2 intensity of the IPS versus coverage, it was determined that four layers of magnesium on Ag(111) is sufficient to completely eliminate the surface band gap

show abstract

Section: Resultssupporting

confidence: 52%

Watching Electrons Transfer from Metals to Insulators using Two Photon Photoemission

Johns

2010

View full text Add to dashboard Cite

show abstract

“…We started with a single crystal Au(111) surface (1 cm diameter) prepared using standard argon ion sputtering and annealing (three cycles: Ar þ 10 mA cm À 2 for 20 min, 773 K for 60 min). A five monolayer epitaxial C 60 film (Sigma-Aldrich, 99.9% purity) was deposited onto the Au(111) surface from Knudsen cell to produce a (2 ffiffi ffi 3 p Â 2 ffiffi ffi 3 p ) R30°super lattice, as confirmed by low-energy electron diffraction 31 . Tc (SigmaAldrich, 99.99% purity) was vapour deposited from a Knudsen cell onto the fullerene-covered Au(111) surface at a sample temperature of 298 K and a growth rate of 1 Å s À 1 .…”

Section: Methodsmentioning

confidence: 99%

Harvesting singlet fission for solar energy conversion via triplet energy transfer

Tritsch

Chan

et al. 2013

Nat Commun

View full text Add to dashboard Cite

The efficiency of a conventional solar cell may be enhanced if one incorporates a molecular material capable of singlet fission, that is, the production of two triplet excitons from the absorption of a single photon. To implement this, we need to successfully harvest the two triplets from the singlet fission material. Here we show in the tetracene (Tc)/copper phthalocyanine (CuPc) model system that triplets produced from singlet fission in the former can transfer to the later on the timescale of 45±5 ps. However, the efficiency of triplet energy transfer is limited by a loss channel due to faster formation (400±100 fs) and recombination (2.6±0.5 ps) of charge transfer excitons at the interface. These findings suggest a design principle for efficient energy harvesting from singlet fission: one must reduce interfacial area between the two organic chromophores to minimize charge transfer/recombination while optimizing light absorption, singlet fission and triplet rather than singlet transfer.

show abstract

“…4(a). The initial intensity drop is fitted with an exponential decay convoluted with the finite width of the laser pulses to metals is reported to have a transfer time in the range of 10-50 fs [40,60], which is comparable to our CT rate for Au. For interfaces dominated by π-orbital coupling, e.g., CT at organic-organic interfaces [49,50,54,55,61], the CT times are around 100 fs, which can be compared to our CT rate for graphene.…”

Section: B Ultrafast Charge-transfer Dynamicsmentioning

confidence: 99%

Effect of Interlayer Coupling on Ultrafast Charge Transfer from Semiconducting Molecules to Mono- and Bilayer Graphene

Wang

Caraiani

et al. 2015

Phys. Rev. Applied

View full text Add to dashboard Cite

Graphene is used as flexible electrodes in various optoelectronic devices. In these applications, ultrafast charge transfer from semiconducting light absorbers to graphene can impact the overall device performance. Here, we propose a mechanism in which the charge-transfer rate can be controlled by varying the number of graphene layers and their stacking. Using an organic semiconducting molecule as a light absorber, the charge-transfer rate to graphene is measured by using time-resolved photoemission spectroscopy. Compared to graphite, the charge transfer to monolayer graphene is about 2 times slower. Surprisingly, the charge transfer to A-B-stacked bilayer graphene is slower than that to both monolayer graphene and graphite. This anomalous behavior disappears when the two graphene layers are randomly stacked. The observation is explained by a charge-transfer model that accounts for the band-structure difference in mono-and bilayer graphene, which predicts that the charge-transfer rate depends nonintuitively on both the layer number and stacking of graphene.

show abstract

Exciton dynamics at molecule-metal interfaces:C60∕Au(111)

Cited by 59 publications

References 49 publications

Watching Electrons Transfer from Metals to Insulators using Two Photon Photoemission

Watching Electrons Transfer from Metals to Insulators using Two Photon Photoemission

Harvesting singlet fission for solar energy conversion via triplet energy transfer

Effect of Interlayer Coupling on Ultrafast Charge Transfer from Semiconducting Molecules to Mono- and Bilayer Graphene

Contact Info

Product

Resources

About