36 research outputs found
Near-infrared exciton-polaritons in strongly coupled single-walled carbon nanotube microcavities
This research was financially supported by the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement No. 306298 (EN-LUMINATE) and under the European Unionâs Horizon 2020 Framework Programme (FP/2014-2020)/ERC Grant Agreement No. 640012 (ABLASE), by EPSRC through the CM-DTC (EP/L015110/1) and by the Scottish Funding Council through SUPA. J.Z. thanks the Alfried Krupp von Bohlen und Halbach-Stiftung via the âAlfried Krupp Förderpreis fĂŒr junge Hochschullehrerâ for general support.Exciton-polaritons form upon strong coupling between electronic excitations of a material and photonic states of a surrounding microcavity. In organic semiconductors the special nature of excited states leads to particularly strong coupling and facilitates condensation of exciton-polaritons at room temperature, which may lead to electrically pumped organic polariton lasers. However, charge carrier mobility and photo-stability in currently used materials is limited and exciton-polariton emission so far has been restricted to visible wavelengths. Here, we demonstrate strong light-matter coupling in the near infrared using single-walled carbon nanotubes (SWCNTs) in a polymer matrix in a planar metal-clad cavity. By exploiting the exceptional oscillator strength and sharp excitonic transition of (6,5) SWCNTs, we achieve large Rabi splitting (> 110 meV), efficient polariton relaxation and narrow band emission (< 15 meV). Given their high charge carrier mobility and excellent photostability, SWCNTs represent a promising new avenue towards practical exciton-polariton devices operating at telecommunication wavelengths.âPublisher PDFPublisher PDFPeer reviewe
Infrared organic light-emitting diodes with carbon nanotube emitters
This research was financially supported by the Volkswagen Foundation (93404), the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement No. 306298 (EN-LUMINATE) and by EPSRC (EP/R010595/1). C.M. acknowledges funding by the European Commission through a Marie SkĆodowska Curie Individual Fellowship (703387). J.Z. thanks the Alfried Krupp von Bohlen und Halbach-Stiftung via the âAlfried Krupp Förderpreis fĂŒr junge Hochschullehrerâ for general support.While organic light-emitting diodes (OLEDs) covering all colors of the visible spectrum have been demonstrated, suitable organic emitter materials in the near-infrared (nIR) beyond 800 nm are still lacking. Here, we demonstrate the first OLED based on single-walled carbon nanotubes (SWCNTs) as the emitter. By using a multi-layer stacked architecture with matching charge blocking and charge transport layers, we achieve narrow band electroluminescence at wavelengths between 1000 nm and 1200 nm, with spectral features characteristic of excitonic and trionic emission of the (6,5) SWCNTs used. We investigate the OLED performance in detail and find that local conduction hot-spots lead to pronounced trion emission. Analysis of the emissive dipole orientation shows a strong horizontal alignment of the SWCNTs with an average inclination angle of 12.9° with respect to the plane, leading to an exceptionally high outcoupling efficiency of 49 %. Our SWCNT-based OLEDs represent a highly attractive platform for emission across the entire nIR.PostprintPeer reviewe
Multispectral electroluminescence enhancement of single-walled carbon nanotubes coupled to periodic nanodisk arrays
The integration of periodic nanodisk arrays into the channel of a light-emitting field-effect transistor leads to enhanced and directional electroluminescence from thin films of purified semiconducting single-walled carbon nanotubes. The maximum enhancement wavelength is tunable across the near-infrared and is directly linked to the periodicity of the arrays. Numerical calculations confirm the role of increased local electric fields in the observed emission modification. Large current densities are easily achieved due to the high charge carrier mobilities of carbon nanotubes and will facilitate new electrically driven plasmonic devices
Electrical pumping and tuning of exciton-polaritons in carbon nanotube microcavities
This research was financially supported by the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement No. 306298 (EN-LUMINATE) and under the European Unionâs Horizon 2020 Framework Programme (FP/2014-2020)/ERC Grant Agreement No. 640012 (ABLASE) and by the Scottish Funding Council (through SUPA). L.T. thanks the EPSRC for support through the CM-DTC (EP/L015110/1). J.Z. thanks the Alfried Krupp von Bohlen und Halbach-Stiftung via the âAlfried Krupp Förderpreis fĂŒr junge Hochschullehrerâ for general support.Exciton-polaritons are hybrid lightâmatter particles that form upon strong coupling of an excitonic transition to a cavity mode. As bosons, polaritons can form condensates with coherent laser-like emission. For organic materials, optically pumped condensation was achieved at room temperature but electrically pumped condensation remains elusive due to insufficient polariton densities. Here we combine the outstanding optical and electronic properties of purified, solution-processed semiconducting (6,5) single-walled carbon nanotubes (SWCNTs) in a microcavity-integrated light-emitting field-effect transistor to realize efficient electrical pumping of exciton-polaritons at room temperature with high current densities (>10âkAâcmâ2) and tunability in the near-infrared (1,060ânm to 1,530ânm). We demonstrate thermalization of SWCNT polaritons, exciton-polariton pumping rates ~104 times higher than in current organic polariton devices, direct control over the coupling strength (Rabi splitting) via the applied gate voltage, and a tenfold enhancement of polaritonic over excitonic emission. This powerful materialâdevice combination paves the way to carbon-based polariton emitters and possibly lasers.PostprintPostprintPeer reviewe
Ultrastrong coupling of electrically pumped near-infrared exciton-polaritons in high mobility polymers
This research was financially supported by the European Research Council under the European Union's Seventh Framework Programme (FP/2007- 2013)/ERC Grant Agreement No. 306298 (EN -LUMINATE) and under the European Unionâs Horizon 2020 Framework Programme (FP/2014- 2020)/ERC Grant Agreement No. 640012 (ABLASE) and by the EPSRC Programme Grant EP/P030017/1. L.T. thanks EPSRC for support through the CM -DTC (EP/L015110/1).Exciton-polaritons are quasiparticles with hybrid lightâmatter properties that may be used in new optoelectronic devices. Here, electrically pumped ultrastrongly coupled exciton-polaritons in a high-mobility donorâacceptor copolymer are demonstrated by integrating a light-emitting field-effect transistor into a metal-clad microcavity. Near-infrared electroluminescence is emitted exclusively from the lower polariton branch, which indicates efficient relaxation. A coupling strength of 24% of the exciton transition energy implies the system is in the ultrastrong coupling regime with a narrow and almost angle-independent emission. The lower polariton energy, which can be adjusted by the cavity detuning, strongly influences the external quantum efficiency of the device. Driving the transistors at ambipolar current densities of up to 4000 A cmâ2 does not decrease the coupling strength or polariton emission efficiency. Cavity-integrated light-emitting field-effect transistors thus represent a versatile platform for polariton emission and polaritonic devices.Publisher PDFPeer reviewe
Brightening of Long, Polymer-Wrapped Carbon Nanotubes by sp Functionalization in Organic Solvents
The functionalization of semiconducting single-walled carbon nanotubes
(SWNTs) with sp defects that act as luminescent exciton traps is a
powerful means to enhance their photoluminescence quantum yield (PLQY) and to
add optical properties. However, the synthetic methods employed to introduce
these defects are so far limited to aqueous dispersions of surfactant-coated
SWNTs, often with short tube lengths, residual metallic nanotubes and poor film
formation properties. In contrast to that, dispersions of polymer-wrapped SWNTs
in organic solvents feature unrivaled purity, higher PLQY and are easily
processed into thin films for device applications. Here, we introduce a simple
and scalable phase-transfer method to solubilize diazonium salts in organic
nonhalogenated solvents for the controlled reaction with polymer-wrapped SWNTs
to create luminescent aryl defects. Absolute PLQY measurements are applied to
reliably quantify the defect-induced brightening. The optimization of defect
density and trap depth results in PLQYs of up to 4 % with 90 % of photons
emitted through the defect channel. We further reveal the strong impact of
initial SWNT quality and length on the relative brightening by sp
defects. The efficient and simple production of large quantities of
defect-tailored polymer-sorted SWNTs enables aerosol-jet printing and
spin-coating of thin films with bright and nearly reabsorption-free defect
emission, which are desired for carbon nanotube-based near-infrared
light-emitting devices
Initialisation et propriétés optiques des plasmons améliorés des carbures de silicium nanostructurés
Nanostructured silicon carbide (SiC) is considered today as a good alternative to the conventional materials for various multidisciplinary applications. In this thesis, SiC nanostructures were elaborated by means of electrochemical etching and laser ablation techniques. The first part of the thesis clarifies size-dependence of optical properties as well as importance of local-field effects onto the photoinduced electronic transitions of SiC nanostructures. In the second part of the thesis strong 15-fold photoluminescence enhancement of SiC nanoparticles is ensured by their near-field interactions with multipolar localized plasmons. Further, 287-fold and 72-fold plasmon-induced enhancement factors of two-photon excited luminescence and second harmonic generation is achieved, respectively. The main physical mechanisms responsible for the observed effects were described by three-dimensional finite-difference time domain simulations. Finally, the coupling effect of luminescent SiC nanoparticles to plasmonic nanostructures is used in the enhanced labelling of biological cells on the planar structures. As a perspective, colloidal plasmonic (Au@SiO2)SiC nanohybrids were elaborated and characterized.Le carbure de silicium (SiC) nanostructurĂ© est considĂ©rĂ© aujourd'hui comme une bonne alternative aux matĂ©riaux traditionnels pour diverses applications multidisciplinaires. Dans cette thĂšse, des nanostructures de SiC ont Ă©tĂ© Ă©laborĂ©es par gravure Ă©lectrochimique et par ablation laser. La premiĂšre partie de cette thĂšse dĂ©crit et explique la dĂ©pendance en taille des propriĂ©tĂ©s optiques ainsi que l'importance des effets de champ local sur les transitions Ă©lectroniques photo-induites des nanostructures de SiC. Dans la seconde partie, il est dĂ©montrĂ© une amplification dâun facteur 15 de lâintensitĂ© de photoluminescence des nanoparticules de SiC par leurs interactions en champ proche avec les plasmons multipolaires localisĂ©es. En outre, un facteur 287 et un facteur 72, induits par le couplage plasmonique, sont obtenus respectivement pour les signaux de luminescence Ă deux photons et de gĂ©nĂ©ration de seconde harmonique. Les principaux mĂ©canismes physiques responsables des effets observĂ©s ont Ă©tĂ© dĂ©crits par des simulations de type diffĂ©rences finies dans le domaine temporel en trois dimensions. Enfin, l'effet de couplage de nanoparticules de SiC luminescentes Ă des nanostructures plasmoniques en structures planes est utilisĂ© pour amĂ©liorer le marquage de cellules biologiques. Une perspective est ouverte sur la rĂ©alisation et les premiĂšres caractĂ©risations de suspension colloĂŻdales de nanohybrides plasmonique (Au@SiO2)SiC
Plasmonic Crystals for Strong LightâMatter Coupling in Carbon Nanotubes
Their
high oscillator strength and large exciton binding energies make single-walled
carbon nanotubes (SWCNTs) highly promising materials for the investigation
of strong lightâmatter interactions in the near infrared and
at room temperature. To explore their full potential, high-quality
cavitiesîžpossibly with nanoscale field localizationîžare
required. Here, we demonstrate the room temperature formation of plasmonâexciton
polaritons in monochiral (6,5) SWCNTs coupled to the subdiffraction
nanocavities of a plasmonic crystal created by a periodic gold nanodisk
array. The interaction strength is easily tuned by the number of SWCNTs
that collectively couple to the plasmonic crystal. Angle- and polarization
resolved reflectivity and photoluminescence measurements combined
with the coupled-oscillator model confirm strong coupling (coupling
strength âŒ120 meV). The combination of plasmonâexciton
polaritons with the exceptional charge transport properties of SWCNTs
should enable practical polariton devices at room temperature and
at telecommunication wavelengths
Photoluminescence enhancement of aligned arrays of single-walled carbon nanotubes by polymer transfer
The photoluminescence of as-grown, aligned single-walled carbon nanotubes (SWNTs) on quartz is strongly quenched and barely detectable. Here we show that transferring these SWNTs to another substrate such as clean quartz or glass increases their emission efficiency by up to two orders of magnitude. By statistical analysis of large nanotube arrays we show at what point of the transfer process the emission enhancement occurs and how it depends on the receiving substrate and the employed transfer polymer. We find that hydrophobic polystyrene (PS) as the transfer polymer results in higher photoluminescence enhancement than the more hydrophilic poly(methyl methacrylate) (PMMA). Possible mechanisms for this enhancement such as strain relief, disruption of the strong interaction of SWNTs with the substrate and localized emissive states are discussed