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Photoexcitation

About: Photoexcitation is a research topic. Over the lifetime, 5874 publications have been published within this topic receiving 134733 citations.


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TL;DR: This work experimentally studies the generated photocurrent at the graphene-metal interface, focusing on the time-resolved photocurrent, the effects of photon energy, Fermi energy and light polarization, and shows that a single framework based on photo-thermoelectric photocurrent generation explains all experimental results.
Abstract: Photoexcitation of graphene leads to an interesting sequence of phenomena, some of which can be exploited in optoelectronic devices based on graphene. In particular, the efficient and ultrafast generation of an electron distribution with an elevated electron temperature and the concomitant generation of a photo-thermoelectric voltage at symmetry-breaking interfaces is of interest for photosensing and light harvesting. Here, we experimentally study the generated photocurrent at the graphene–metal interface, focusing on the time-resolved photocurrent, the effects of photon energy, Fermi energy and light polarization. We show that a single framework based on photo-thermoelectric photocurrent generation explains all experimental results.

66 citations

Journal ArticleDOI
TL;DR: In this paper, the photoexcitation of surface plasmons at an Ag-SiO2 interface is numerically demonstrated to yield a 50% coupling efficiency from a Gaussian beam into surface plasmon voltages and currents.
Abstract: The efficient generation of surface plasmons from free-space optical waves is still an open problem in the field. Here we present a methodology and optimized design for a grating coupler. The photoexcitation of surface plasmons at an Ag-SiO2 interface is numerically demonstrated to yield a 50% coupling efficiency from a Gaussian beam into surface plasmon voltages and currents.

66 citations

Journal ArticleDOI
TL;DR: It is shown that excitation in high-energy states generates electron and hole wave functions with reduced overlap, which likely act as precursors for the polaron pairs in oligomers.
Abstract: We investigate the role of excess excitation energy on the nature of photoexcitations in donor–acceptor π-conjugated materials. We compare the polymer poly(2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta[1,2-b;3,4-b′]dithiophene)-4,7-benzo[2,1,3]thiadiazole) (PCPDTBT) and a short oligomer with identical constituents at different excitation wavelengths, from the near-infrared up to the ultraviolet spectral region. Ultrafast spectroscopic measurements clearly show an increased polaron pair yield for higher excess energies directly after photoexcitation when compared to the exciton population. This effect, already observable in the polymer, is even more pronounced for the shorter oligomer. Supported by quantum chemical simulations, we show that excitation in high-energy states generates electron and hole wave functions with reduced overlap, which likely act as precursors for the polaron pairs. Interestingly, in the oligomer we observe a lifetime of polaron pairs which is one order of magnitude longer. We suggest th...

66 citations

Journal ArticleDOI
TL;DR: In this paper, nonequilibrium vibrational excitations of para-nitroaniline (PNA) occurring after internal conversion from the photoexcited charge transfer state are studied by picosecond anti-Stokes Raman scattering.
Abstract: Nonequilibrium vibrational excitations of para-nitroaniline (PNA, 4-nitroaniline) occurring after internal conversion from the photoexcited charge transfer state are studied by picosecond anti-Stokes Raman scattering. Vibrational excess populations with distinctly different picosecond rise and decay times are found for a number of modes with frequencies between 860 and 1510 cm−1, including the overtone of a non-Raman active mode. A nonthermal distribution of vibrational populations exists up to about 6 ps after photoexcitation. The time-resolved experiments are complemented by steady-state infrared and Raman measurements as well as calculations based on density functional theory, providing a detailed analysis of the steady-state vibrational spectra of PNA and two of its isotopomers. A weakly Raman active vibration at about 1510 cm−1 displays the fastest rise time and a pronounced excess population and—thus—represents the main accepting mode. We suggest that an out-of-plane mode giving rise to the overtone...

66 citations

Journal ArticleDOI
TL;DR: In this article, free base porphyrin molecules form well-defined and ordered nanoclusters in mixed solvents with absorption characteristics that significantly differ from those of the monomer form.
Abstract: Free base porphyrin molecules form well-defined and ordered nanoclusters in mixed solvents with absorption characteristics that significantly differ from those of the monomer form. These self-assembled crystallites in acetonitrile/toluene (9 ∶ 1, v/v) can be deposited as thin films on a nanostructured TiO2 electrode using an electrophoretic technique. This porphyrin cluster assembly is highly photoactive and capable of undergoing charge separation under visible light excitation. Photoexcitation of the porphyrin film electrode assembly in a photoelectrochemical cell with visible light produces relatively high photocurrent generation. A maximum photocurrent of 0.15 mA cm−2 and a photovoltage of 250 mV were attained using the I3−/I− redox couple. The electron flow to the TiO2 electrode can be facilitated by application of a positive potential. An incident photon-to-photocurrent generation efficiency (IPCE) of 2.0% has been achieved at an applied bias potential of 0.2 V vs. SCE. The broad photoresponse of these crystallites throughout the visible range as well as the ease of assembling them on the electrode surface opens up new avenues for harvesting a wide wavelength range of solar light.

66 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023249
2022529
2021221
2020204
2019183
2018256