Several people have been working on this for a while. Impact of phonon dispersion on nonlocal electronphonon. Quantum localization and delocalization of charge carriers. The latter mechanism is affected by the charge reorganization energy which depends on the hole electron coupling with. Enhancement of the electronphonon scattering induced by. B at high magnification, the internal lattice structure of the nc building blocks is reso. Asite cations, as spacers, allow various metal halide assemblies, but the stacking pattern and the influence of their collective behavior on the properties of the resultant materials remain ambiguous. While the nonlocal electron phonon interactions can in general be divided into contributions from. Recent studies point to the impact that the dispersion of both optical and acoustic phonons can have on the nonlocal electron phonon couplings in organic molecular semiconductors.
Employing a firstprinciples approach, we compute the changes in the selfconsistent kohnsham potential corresponding to different phonon modes and go on to obtain the carrier phonon coupling matrix elements vertex. We then examine the electronic structure at interfaces between an organic layer and a metal or. The coupling between nuclear vibrations and electronic excitations electron. This lecture addresses the consequences of electronphonon coupling in both the. Stojanovic submitted on 14 apr 2012, last revised 19 sep 2012 this version, v3 abstract. We discuss, in the context of a tightbinding description, how the electronic and chargetransport properties in single crystals of molecular organic semiconductors are affected by the nonlocal electron phonon coupling to both acoustic and optical lattice vibrations. A substantial amount of evidence indicates a relevant role played by the nonlocal electron phonon couplings in the mechanism of charge transport in organic semiconductors.
Charge transport in organic semiconductors lehrstuhl ep2 uni. Pdf impact of phonon dispersion on nonlocal electron. To understand which specific phonon modes contribute most strongly to the electron phonon coupling and ensuing thermal energetic disorder in some of the most widely studied highmobility molecular semiconductors, stateof. In section 4, we present an overview of the models that have been reported to describe the chargetransport mechanisms in molecular crystals and disordered organic materials. Carrier transport calculations of organic semiconductors. Electronphonon coupling phonon scattering electron. Direct observation of electron phonon coupling and slow. Electronicstructure theory of organic semiconductors. Electronphonon coupling in highly doped n type silicon. Phase phonons and intramolecular electronphonon coupling. Electronphonon coupling in hybrid lead halide perovskites. We have calculated the relevant intermolecular charge transfer parameters that determine whether a.
General theory of electronic transport in molecular. Section iii explains how the optical absorption spectrum is affected by. Recent theoretical studies suggest that the modulation of the electronic couplings transfer integrals between adjacent molecules by lattice vibrations, i. In this work, we compute the nonlocal electron phonon coupling for the prototypical molecular semiconductors rubrene and tetracene using the phonon modes obtained. While in the case of rubrene, the coupling between charge carriers and low frequency intermolecular modes is suf. Polaron transport in organic semiconductors quantsim09, warwickuk, 27 aug 2009 1 polaron transport in organic semiconductors. Organic semiconductors overcome many of inorganic disadvantages such as high cost on a large scale in either preparation or device fabrication and. Free carrier emergence and onset of electronphonon.
This observation points out a strong size dependence of the electron. Organic semiconductors are also sensitive to polaronic effects, which is particularly relevant in the design of organic solar cells that effectively transport charge. Holephonon coupling effect on the band dispersion of. However, a direct evidence of the expected impact of the charge phonon coupling on the band dispersion of organic semiconductors. Impact of phonon dispersion on nonlocal electronphonon couplings in organic semiconductors. The profile factor which is related to the disymetry, is shown to have the signes of the matrix elements of the electron phonon interaction. To understand which specific phonon modes contribute most strongly to the electron phonon coupling and ensuing thermal energetic disorder in some of the most widely studied high. We consider electronholephonon coupling in crystalline organic semiconductors, using naphthalene for our case study. Electron phonon coupling in cdsecds coreshell quantum dots chen lin, ke gong, david f. It is valid for arbitrary electronic and phonon bandwidths and for arbitrary electron phonon coupling strength, yielding smallpolaron theory for narrow electronic. This model is based on the assumption that the charge carrier is localized, i. Electronphonon coupling in crystalline organic semiconductors. The electronic and electrical properties of crystalline organic semiconductors, such as the dispersions of the electronic bands and the dependence of chargecarrier mobility on temperature, are. Pdf from charge transport parameters to charge mobility in.
In this work, we calculated the eph coupling elements throughout the whole brillouin zone in. Electronphonon coupling epc also provides in a fundamental way an attractive electron electron interaction, which is always present and, in many metals, is the origin of the electron pairing underlying the macroscopic quantum phenomenon of superconductivity. Electron coupling to optical phonons is observed as periodic spectral modulations in the pumpprobe data of both films. Microscopic evidence for nonpolaronic charge carriers.
Semiconductor x0 simple vibrational spectrum metal. We consider electron phonon coupling in crystalline organic semiconductors, using naphthalene for our case study. Enhanced electronphonon coupling for a semiconductor. A computational protocol for the calculation of local holstein and nonlocal peierls carrier phonon coupling in molecular organic semiconductors is presented and. Kelley, and anne myers kelley chemistry and chemical biology, university of california, merced, 5200 north lake road, merced, california 95343, united states semiconductor nanocrystals consisting of a core of one material and one or. Pdf the effects of different electronphonon couplings. Optical conductivity and optical effective mass in a high. The analysis is based on a theory originally developed for obtaining for metal surfaces, but which here is adapted to the more complicated cases of layered chalcogenide semiconductors and systems that can be considered as having di erent dimensions such as 1d cdws and quasicrystals. We consider electronphonon coupling in crystalline organic semiconductors, using naphthalene for our case study. Section 3 deals with a detailed description of the chargetransport param eters. Polaron stabilization by cooperative lattice distortion. Despite wide interest in organic molecular crystals and the recognition that electron phonon eph coupling strength crucially determines the nature of charge carriers in these materials, abinitio studies of eph coupling elements in these materials are still lacking. Spectral and transport properties of small molecule singlecrystal organic semiconductors have been theoretically analyzed focusing on oligoacenes, in particular on the series from naphthalene to rubrene and pentacene, aiming to show that the inclusion of different electron phonon couplings is of paramount importance to interpret accurately the properties of prototype organic semiconductors. It is an electrically neutral quasiparticle that exists in insulators, semiconductors and some liquids.
The frontier of research in organic semiconductors is attempting to get a complete picture of electron transport by understanding intramolecular and intermolecular vibrations or phonons and electronphonon coupling. The exciton is regarded as an elementary excitation of condensed matter that can transport energy without transporting net electric charge. We evaluate the validity of the commonly assumed polaron hopping model for some of the most popular organic semiconductors, rubrene, pentacene, and c60. Importantly, an adequate description of the electronic and chargetransport properties of organic. Moreover, the contributions of acoustic phonons to the overall strength of nonlocal electronphonon couplings are calculated to be quantitatively very significant for parallelstacked dimers, as high as 40% for holes and 47% for electrons. An exciton is a bound state of an electron and an electron hole which are attracted to each other by the electrostatic coulomb force. The unperturbed phonon hamiltonian hphis of course just the sum of 3n independent harmonic oscillators in 2nd quantized form, and the bare coulomb matrix element in hcoulis vq4. Stacking effects on electronphonon coupling in layered. Overall, our results conclusively demonstrate that electron phonon coupling in hybrid lead halide perovskites follows a classic bandstructure picture for polar inorganic semiconductors, which. Electron phonon coupling in crystalline organic semiconductors. Symmetry effects on nonlocal electronphonon coupling in. In this paper, we derive a rigorous theory of the exciton phonon coupling. Organic semiconductors overcome many of inorganic disadvantages such as high cost on a large scale in either preparation or device fabrication and the low compatibility with flexible substrates 1.
Dntv25 as an example of a highmobility organic semiconductor. Nonlocal electronphonon coupling in organic semiconductor. However, a detailed understanding of this mechanism is still missing. Electron phonon coupling in cdsecds coreshell quantum. Pdf impact of phonon dispersion on nonlocal electronphonon.
Chasing the killer phonon mode for the rational design. We compare the magnitude of electron phonon coupling of organic semiconductors to that of covalentbond systems. Data in olive are obtained from fobsh with electronic coupling between. Symmetry effects on nonlocal electron phonon coupling in organic semiconduc tors li, yuan. Electrons interact with these displacements, and this interaction is known as electron phonon coupling. The vibrational excitations responsible for the remarkable series of infrared absorption bands observed in the organic linear chain semiconductor teatcnq 2 are identified to be the phase phonons which result from the coupling of the conduction electron molecular orbital to the totally symmetric vibrations of the tcnq molecule. Traditionally in semiconductors one parametrizes electron. Phonon coupling and slow vibrational relaxation in organic. Intermolecular charge transfer parameters, electronphonon. A temperaturedependent study of rutile ti o 2 by firstprinciples theory and twophoton photoemission article pdf available december 2019 with. Electronphonon coupling is a major decoherence mechanism, which often causes scattering and energy dissipation in semiconductor electronic systems.
The effects of different electron phonon couplings on the spectral and transport properties of small molecule singlecrystal organic semiconductors. The effects of different electronphonon couplings on the. Interaction of charge carriers with lattice vibrations in. The electron phonon coupling patterns in real space are seen to have a direct and significant impact on the interactions in reciprocal space. Our findings demonstrate the importance of aspects that are usually missing in current transport models. Here, the cation stacking effects in the 2d perovskite single crystals, with the focus on the electronphonon interaction is investigated. Straus, sebastian hurtado parra, natasha iotov, julian gebhardt, andrew m. We consider electron hole phonon coupling in crystalline organic semiconductors, using naphthalene for our case study. The dynamic interaction between the traveling charges and the molecular vibrations is critical for the charge transport in organic semiconductors. An improved general theory of electronic transport in molecular crystals with local linear electron phonon coupling is presented. Effects of different electronphonon couplings on spectral and. The electronphonon interaction of lowdimensional and.