In this Letter we show that the strong coupling between a disordered set of molecular emitters and surface plasmons leads to the formation of spatially coherent hybrid states extended on acroscopic distances. Young type interferometric experiments performed on a system of J-aggregated dyes spread on a silver layer evidence the coherent emission from different molecular emitters separated by several microns. The coherence is absent in systems in the weak coupling regime demonstrating the key role of the hybridization of the molecules with the plasmon.
Inorganic-organic perovskites semiconductors are becoming increasingly interesting due to their remarkable optical properties, such as a high photoluminescence quantum yield and the possibility to show optical gain in a broad range of wavelengths. We have here simulated microcavities that embed MaPBI3 and 2D hybrid organic inorganic perovskite semiconductors by sandwiching such active layers between periodic, aperiodic and disordered photonic structures. We have carefully considered the refractive index dispersion of all the materials employed, such silicon dioxide, titanium dioxide and the pe…
We report inelastic light scattering from underdamped plasmons in azetidinium lead bromide (AzPbBr3). The plasmons are very strongly temperature dependent and serve as a soft mode for the semiconductor-insulator phase transition near TC » 150 K, demonstrating a continuous decrease in hole concentration np(T) by at least a factor of four and implying a nearly tricritical transition. The plasmon frequency and linewidth agree with independent measurements, and the impedance analysis reveals a frequency dependence (modelled by a constant phase element, CPE) that can be identified as due to electro…
We consider the resonant energy transfer from a two-dimensional Wannier exciton (donor) to a Frenkel exciton of a molecular crystal overlayer (acceptor) when the active medias are separated by a metallic layer, possibly an electrode. We characterize the effect of the surface plasmon on this process. Using realistic values of material parameters, we show that it is possible to change the transfer rate within typically a factor of 5 (up to 44 according to geometrical configuration). We then take into account the quenching of the organic luminescence due to the proximity with the metal. This latt…
Understanding the charge carrier transport in the disordered organic molecular semiconductors is a fascinating and still unresolved problem in modern condensed-matter physics, yet has an extremely important bearing on their application in ``plastic'' based field effect transistor, light emitting diodes and lasers. The most contentious issue in this subject is the nature of the charge carriers i.e. whether they are bare electrons or dressed electrons, known as polarons. Here we show for the first time, by means of simple experiments that polaron moving in static disorder is responsible for char…
The incorporation of noble metal nanoparticles, displaying localized surface plasmon resonance, in the active area of donor-acceptor bulk-heterojunction organic photovoltaic devices is an industrially compatible light trapping strategy, able to guarantee better absorption of the incident photons and give an efficiency improvement between 12% and 38%. In the present work, we investigate the effect of Au and Ag nanoparticles blended with P3HT: PCBM on the P3HT crystallization dynamics by synchrotron grazing incidence X-ray diffraction. We conclude that the presence of (1) 80nm Au, (2) mix of 5nm…
Hybrid organic-inorganic perovskites (HOIPs) have emerged to the forefront of optoelectronic materials advancement in the past few years. Due to the nature of organic compounds within the perovskite structure, its optoelectronic properties are affected by complex interaction and correlation effects between the organic and inorganic ions. Using spectroscopic ellipsometry, we observe two broad plasmonic excitation from the calculated loss function (LF) -Im[\varepislon^{-1} (ω)], peak A' and B' at 3.28 eV and 4.26 eV, respectively.The presence of these two asymmetric peaks in the spectroscopic el…
Manipulating strong light-matter interaction in semiconductor microcavities is crucial for developing high-performance exciton polariton devices with great potentials in next-generation all-solid state quantum technologies. In this work, we report surface plasmon enhanced strong exciton-photon interaction in CH3NH3PbBr3 perovskite nanowires. Characteristic anti-crossing behaviors, indicating Rabi splitting energy up to ~ 560 meV, are observed near exciton resonance in hybrid semiconductor-insulator-metallic waveguide cavity at room temperature. An exciton-photon coupling strength enhancement f…
Metal/semiconductor interfaces govern the operation of semiconductor devices through the formation of charge injection barriers that can be controlled by tuning the metal work function. However, the controlling ability is typically limited to being static. We show that a dynamic nature can be imparted to the interfaces using electrode surface modification with a structurally disordered molecular monolayer. The barrier height at the interfaces is altered significantly in a reversible way by an external electric field. As a result, a dramatic change in the carrier transport properties through th…
We study collective plasmon excitations and screening of disordered single- and bilayer black phosphorus beyond the low energy continuum approximation. The dynamical polarizability of phosphorene is computed using a tight-binding model that properly accounts for the band structure in a wide energy range. Electron-electron interaction is considered within the Random Phase Approximation. Damping of the plasmon modes due to different kinds of disorder, such as resonant scatterers and long-range disorder potentials, is analyzed. We further show that an electric field applied perpendicular to bilay…
In this article, we present an alternative method for simulating charge transport in disordered organic materials by using a buffer lattice at the boundary. This method does not require careful tracking of carrier's hopping pattern across boundaries. Suitability of this method is established by reproducing the field dependence of mobility, carrier relaxation and carrier diffusion in disordered organic systems obtained by simulating the charge transport for the full length of the systems along the field direction without and boundary condition. The significance of the buffer lattice is emphasiz…
Computer simulation of the hopping charge transport in disordered organic materials has been carried out explicitly taking into account charge-charge interactions. This approach provides a possibility to take into account dynamic correlations that are neglected by more traditional approaches like mean field theory. It was found that the effect of interaction is no less significant than the usually considered effect of filling of deep states by non-interacting carriers. It was found too that carrier mobility generally increases with the increase of carrier density, but the effect of interaction…
Effect of energetic disorder on charge carrier transport in organic materials has been reexamined. A reliable method for mobility calculation and subsequent evaluation of relevant disorder parameters has been discussed. This method is well suited for a direct calculation of the magnitude of dipolar disorder $σ_\textrm{dip}$ in polar organic materials from the current transients. Calculation of $σ_\textrm{dip}$ for several transport materials with varying concentration of polar dopants gives concentration dependences that are in reasonable agreement with theoretical predictions. A possible solu…
The generation mechanisms of electron spin polarization (ESP) of charge carriers (electrons and holes, called "doublets") in doublet-doublet recombination and triplet-doublet quenching in disordered organic semiconductors are analyzed in detail. The ESP is assumed to result from quantum transitions between the states of the spin Hamiltonian of the pair of interacting particles. The value of the ESP is essentially determined by the mechanism of relative motion of particles. In our work we have considered the cage and free diffusion models. The effect of possible attractive spin-independent inte…
We provide a phenomenological formula which describes the low-frequency optical absorption of charge carriers in disordered systems with localization. This allows to extract, from experimental data on the optical conductivity, the relevant microscopic parameters determining the transport properties, such as the carrier localization length and the elastic and inelastic scattering times. This general formula is tested and applied here to organic semiconductors, where dynamical molecular disorder is known to play a key role in the transport properties. The present treatment captures the basic ide…
Charge transport properties in organic semiconductors are determined by two kinds of microscopic disorders, namely energetic disorder related to the distribution of localized states and the spatial disorder related to the morphological features of the material. From a semi-classical picture, the charge transport properties are crucially determined by both the carrier mobility and the electrostatic field distribution in the material. Although the effect of disorders on carrier mobility has been widely studied, how electrostatic field distribution is distorted by the presence of disorders and it…
We present a simple method to prove the presence of an organic shell around silver nanoparticles. This method is based on the comparison between optical extinction measurements of isolated nanoparticles and Mie calculations predicting the expected wavelength of the Localized Surface Plasmon Resonance of the nanoparticles with and without the presence of an organic layer. This method was applied to silver nanoparticles which seemed to be well protected from oxidation. Further experimental characterization via Surface Enhanced Raman Spectroscopy (SERS) measurements allowed to identify this prote…
We suggest universal expressions for the rates of charge transition between molecules in organic disordered semiconductors, which differ between electrons and holes. The donor and acceptor molecules (monomers) are represented in terms of their frontier orbitals, with asymptotic tails reflecting the different asymptotic potential wells which bind different charge carriers. This model predicts an asymmetry of the tunnel factors and the interaction with phonon field with respect to electrons and holes, leading to different formulas for the transition rates and the thermal mobility of the differen…
Simulations of charge transport in amorphous semiconductors are often performed in microscopically sized systems. As a result, charge carrier mobilities become system-size dependent. We propose a simple method for extrapolating a macroscopic, nondispersive mobility from the system-size dependence of a microscopic one. The method is validated against a temperature-based extrapolation [Phys. Rev. B 82, 193202 (2010)]. In addition, we provide an analytic estimate of system sizes required to perform nondispersive charge transport simulations in systems with finite charge carrier density, derived f…
We address the role of excitonic coulping on the nature of photoexcitations in the conjugated polymer regioregular poly(3-hexylthiophene). By means of temperature-dependent absorption and photoluminescence spectroscopy, we show that optical emission is overwhelmingly dominated by weakly coupled H-aggregates. The relative absorbance of the 0-0 and 0-1 vibronic peaks provides a powerfully simple means to extract the magnitude of the intermolecular coupling energy, approximately 5 and 30 meV for films spun from isodurene and chloroform solutions respectively.
Electrically stimulated switching of a charge injection barrier at the interface between an organic semiconductor and an electrode modified with a disordered monolayer (DM) is studied by using various benzenethiol derivatives as DM molecules. The switching behavior is induced by a structural change in the DM molecules, and is manifested as a reversible inversion of the polarity of DM-modified Au electrode/rubrene/DM-modified Au electrode diodes. The switching direction is found to be dominantly determined by the push-back effect of the thiol bonding group, while the terminal group modulates th…
Charge transport in disordered organic semiconductors occurs by hopping of charge carriers between localized sites that are randomly distributed in a strongly energy dependent density of states. Extracting disorder and hopping parameters from experimental data like temperature dependent current-voltage characteristics typically relies on parametrized mobility functionals that are integrated in a drift-diffusion solver. Surprisingly, the functional based on the extended Gaussian disorder model (eGDM) has been extremely successful at this, despite it being based on the assumption of nearest neig…
Characteristic properties of magnetic field effects on spin selective geminate and bulk electron-hole polaron pair (PP) recombination are analyzed in detail within the approach based on the stochastic Liouville equation. Simple expressions for the magnetic field (B) dependence of recombination yield and rate are derived within two models of relative PP motion: free diffusion and diffusion in the presence of well (cage). The spin evolution of PPs is described taking in account the relaxation induced by hyperfine interaction, anisotropic part of the Zeeman interaction induced, as well as $Δg$-me…
The influence of ordered regions (micro crystallites and aggregates) in the other wise disordered polymer host matrix on field and temperature dependence of mobility (μ) has been simulated. Increase in concentration of ordered regions leads to increase in magnitude of mobility and in high field regime the saturation of the mobility occurs at lower electric field strength. The influence of different mean and standard deviation of Gaussian density of states (DOS) of ordered regions on the field dependence of mobility was studied and found to be significant only at higher concentrations. Weak inf…
We have studied the properties of the prototype hybrid organic-inorganic perovskite $\text{CH}_3^{}\text{NH}_3^{}\text{PbI}_3^{}$ using relativistic density functional theory (DFT). For our analysis we introduce the concept of $\text{CH}_3^{}\text{NH}_3^+$ "pair modes", that is, characteristic relative orientations of two neighboring $\text{CH}_3^{}\text{NH}_3^+$ cations. In our previous work [Phys. Rev. B \textbf{94}, 045201 (2016)] we identified two preferential orientations that a single $\text{CH}_3^{}\text{NH}_3^+$ cation adopts in a unit cell. The total number of relevant pairs can be re…
Materials based on the cubic perovskite unit cell continue to provide the basis for technologically important materials with two notable recent examples being lead-based relaxor piezoelectrics and lead-based organic-inorganic halide photovoltaics. These materials carry considerable disorder, arising from site substitution in relaxors and molecular vibrations in the organic-inorganics, yet much of our understanding of these systems derives from the initial classic work of Prof. Roger A. Cowley, who applied both theory and neutron scattering methods while at Chalk River Laboratories to the study…
In this work we use a three-dimensional Pauli master equation to investigate the charge carrier mobility of a two-phase system, which can mimic donor-acceptor and amorphous- crystalline bulk heterojunctions. Our approach can be separated into two parts: the morphology generation and the charge transport modeling in the generated blend. The morphology part is based on a Monte Carlo simulation of binary mixtures (donor/acceptor). The second part is carried out by numerically solving the steady-state Pauli master equation. By taking the energetic disorder of each phase, their energy offset and do…
The excitation spectrum and the collective modes of graphene antidot lattices (GALs) are studied in the context of a $π$-band tight-binding model. The dynamical polarizability and dielectric function are calculated within the random phase approximation. The effect of different kinds of disorder, such as geometric and chemical disorder, are included in our calculations. We highlight the main differences of GALs with respect to single-layer graphene (SLG). Our results show that, in addition to the well-understood bulk plasmon in doped samples, inter-band plasmons appear in GALs. We further show …
1. Introduction 2. Molecular dynamics simulation of amorphous carbon structures 3. Atomistic simulation of the bombardment process during the BEN phase of diamond CVD 4. Growth of amorphous silicon 5. One-dimensional hopping in disordered organic solids
The plasmonic properties of vacuum evaporated nanostructured gold thin films having different types of nanoparticles are presented. The films with more than 6 nm thickness show presence of nanorods having non cylindrical shape with triangular base. Two characteristics plasmon bands have been recoreded in absorption spectra. First one occurs below 500 nm and other one at higher wavelength side. Both the peaks show dependence on the dielectric property of surroundings. The higher wavelength localized surface plasmon resonance (LSPR) peak shifts to higher wavelength with an increase in the nanopa…
We have investigated the charge carrier transport in organic molecular semiconductors. It has been found that mobility is a function of electric field and temperature due to hopping conduction. Several theoretical models for charge transport in disordered solids have been debated over the role of spatial and energetic correlation in these systems and such correlations have been recently shown to explain the universal electric field dependence of mobility. We have compared and evaluated the applicability of different theoretically proposed models using very simple experimental results and based…
We explore polaronic quantum transport in three-dimensional models of disordered organic crystals with strong coupling between electronic and vibrational degrees of freedom. By studying the polaron dynamics in a static disorder environment, temperature dependent mobilities are extracted and found to exhibit different fingerprints depending on the strength of the disorder potential. At low temperatures and for strong enough disorder, coherence effects induce weak localization of polarons. These effects are reduced with increasing temperature (thermal disorder) resulting in mobility increase. Ho…
A relation derived from the Kubo formula shows that optical conductivity measurements below the gap frequency in doped semiconductors can be used to probe directly the time-dependent quantum dynamics of charge carriers. This allows to extract fundamental quantities such as the elastic and inelastic scattering rates, as well as the localization length in disordered systems. When applied to crystalline organic semiconductors, an incipient electron localization caused by large dynamical lattice disorder is unveiled, implying a breakdown of semiclassical transport.
Effect of static charges on charge carrier transport in disordered organic materials is considered. Long range nature of Coulomb interaction requires to take into consideration a finite thickness of the transport layer. Presence of conducting electrodes significantly modifies properties of organic medium, removes a long range Coulomb divergence, and makes it possible to calculate in finite form statistical properties of organic medium (with nonzero total charge density), relevant for transport characteristics. A special attention is paid to the particular case of charge induced disorder - a di…
Plasmons, quantized collective oscillations of electrons, have been observed in metals and semiconductors. Such massive electrons have been the basic ingredients of research in plasmonics and optical metamaterials.1 Also, Dirac plasmons have been observed in graphene, two-dimensional electron systems and topological insulators (TIs). A nontrivial Z2 topology of the bulk valence band leads to the emergence of massless Dirac fermions on the surface in TIs.2,3 Although Dirac plasmons can be formed through additional grating or patterning, their characteristics promise novel plasmonic metamaterial…
Polaritons are quasiparticles arising from the strong coupling of electromagnetic waves in cavities and dipolar oscillations in a material medium. In this framework, localized surface plasmon in metallic nanoparticles defining optical nanocavities have attracted increasing interests in the last decade. This interest results from their sub-diffraction mode volume, which offers access to extremely high photonic densities by exploiting strong scattering cross-sections. However, high absorption losses in metals have hindered the observation of collective coherent phenomena, such as condensation. I…
The definition of plasmon at the microscopic scale is far from being understood. Yet, it is very important to recognize plasmonic features in optical excitations, as they can inspire new applications and trigger new discoveries by analogy with the rich phenomenology of metal nanoparticle plasmons. Recently, the concepts of plasmonicity index and the generalized plasmonicity index (GPI) have been devised as computational tools to quantify the plasmonic nature of optical excitations. The question may arise whether any strong absorption band, possibly with some sort of collective character in its…
Organic-inorganic coupling in the hybrid lead-halide perovskite is a central issue in rationalizing the outstanding photovoltaic performance of these emerging materials. Here we compare and contrast the evolution of structure and dynamics of the hybrid CH3NH3PbBr3 and the inorganic CsPbBr3 lead-halide perovskites with temperature, using Raman spectroscopy and single-crystal X-ray diffraction. Results reveal a stark contrast between their order-disorder transitions, abrupt for the hybrid whereas smooth for the inorganic perovskite. X-ray diffraction observes an intermediate incommensurate phase…
The list of two dimensional Dirac systems with a tilt in their Dirac cone spectrum is expanding, and now in addition to organic system $α$(BEDT-TTF)$_2$I$_3$ includes the two dimensional $8Pmmn$-borophene sheet, which allows for controlled doping by the gate voltage. We analytically calculate the polarization function of tilted Dirac cone for arbitrary tilt parameter, $0\le η<1$, and arbitrary doping. This enables us to find two interesting plasmonic effects solely caused by the tilt: (i) In addition to the standard plasmon oscillations, strong enough tilt, induces an additional linearly dispe…
Metal--organic frameworks (MOFs) are a family of chemically diverse materials, with applications in a wide range of fields covering engineering, physics, chemistry, biology and medicine. Research so far has focused almost entirely on crystalline structures, yet a clear trend has emerged shifting the emphasis onto disordered states of MOFs, including "defective by design" crystals, as well as amorphous phases such as glasses and gels. Here we introduce a MOF liquid, a strongly associated liquid obtained by melting a zeolitic imidazolate framework (ZIF), with retention of chemical configuration,…
The charge carrier drift mobility in disordered semiconductors is commonly graphically extracted from time-of-flight (ToF) photocurrent transients yielding a single transit time. However, the term transit time is ambiguously defined and fails to deliver a mobility in terms of a statistical average. Here, we introduce an advanced computational procedure to evaluate ToF transients, which allows to extract the whole distribution of transit times and mobilities from the photocurrent transient, instead of a single value. This method, extending the work of Scott et al. (Phys. Rev. B 46, 8603), is ap…
Metal-organic frameworks comprehend a wide class of hybrid organic-inorganic materials with general structure A$_m$BX$_n$, with $A$ and $X$ being organic molecules and B a metal cation. This often results in enhanced structural flexibility and new functionalities. Hybrid perovskites ABX$_3$ are a well-known example.} In an Iron-based perovskites, (DMA)Fe^{II-III}(COOH)_3, dimethylammonium (DMA) molecules are organized in a hexagonal structure. They are orientationally disordered at high temperatures, but order at around $T=100$~K in a peculiar toroidal pattern. Recent experimental and theoreti…
