From a numerical solution of the master equation for hopping transport in disordered energy landscape with Gaussian density states, we determine dependence charge-carrier mobility on temperature, carrier density, and electric field. Experimental current-voltage characteristics devices based semiconducting polymers are excellently reproduced this unified description mobility. At room temperature it is mainly that plays an important role, whereas at low temperatures high fields field becomes...

We present a mechanism for the recently discovered magnetoresistance in disordered pi-conjugated materials, based on hopping of polarons and bipolaron formation, presence random hyperfine fields hydrogen nuclei an external magnetic field. Within simple model we describe field dependence density. Monte Carlo simulations including on-site longer-range Coulomb repulsion show how this leads to positive negative magnetoresistance. Depending branching ratio between formation or dissociation rates,...

It has recently been demonstrated that the hopping mobility in semiconducting organic materials depends on charge-carrier concentration. We have analyzed this effect within framework of six existing semianalytical models, for case a Gaussian density states (DOS). These models were either not applied earlier to DOS, or are shown require major modification. The is constant below certain concentration, which decreases with increasing ratio $\stackrel{\ifmmode \hat{}\else \^{}\fi{}}{s}$ width...

Abstract Recent success in achieving highly stable Rb‐containing organolead halide perovskites has indicated the possibility of incorporating small monovalent cations, which cannot fit lead‐halide cage with an appropriate tolerance factor, into perovskite lattice while maintaining a pure “black” phase. In this study, through combined experimental and theoretical investigation by density functional theory (DFT) calculations on incorporation extrinsic alkali cations (Rb + , K Na Li )...

Abstract Organic field‐effect transistors (OFETs) are considered in technological applications for which low cost or mechanical flexibility crucial factors. The environmental stability of the organic semiconductors used OFETs has improved to a level that is now sufficient commercialization. However, serious problems remain with under operation. causes this have remained elusive many years. Surface potentiometry together theoretical modeling provide new insights into mechanisms limiting...

Mixed halide perovskites that are thermodynamically stable in the dark demix under illumination. This is problematic for their application solar cells. We present a unified thermodynamic theory this light-induced segregation based on free energy lowering of photocarriers funnelling to nucleated phase with different composition and lower band gap than parent phase. apply sequence mixed iodine-bromine perovskites. The spinodals separating metastable unstable regions composition-temperature...

We present a theoretical description of polaron bandwidth narrowing in organic molecular crystals. Based on solution Holstein-Peierls model for tightly bound electrons interacting with phonons, an explicit expression the temperature dependence electronic bandwidths is found. This formula generalizes result Holstein theory by treating local and nonlocal electron-phonon coupling equal footing. The usefulness method demonstrated studies oligo-acene crystals from which microscopic insight into...

The electrical instability of organic field-effect transistors is investigated. We observe that the threshold-voltage shift (see figure) shows a stretched- exponential time dependence under an applied gate bias. activation energy 0.6 eV common for our and all other reported so far. constant supports charge trapping by residual water as origin.

We present an ab initio description of charge-carrier mobilities in organic molecular crystals high purity. Our approach is based on Holstein’s original concept small-polaron bands but generalized with respect to the inclusion nonlocal electron–phonon coupling. By means explicit expression for as a function temperature combination calculations material parameters, we demonstrate predictive power our theory by applying it naphthalene. The results show good qualitative agreement experiment and...

We present a theory for spin diffusion in disordered organic semiconductors, based on incoherent hopping of charge carrier and coherent precession its an effective magnetic field, composed the random hyperfine field hydrogen nuclei applied field. From Monte Carlo simulations analysis waiting-time distribution we predict surprisingly weak temperature dependence, but considerable magnetic-field dependence spin-diffusion length. show that both predictions are agreement with experiments valves.

Abstract The outstanding optoelectronics and photovoltaic properties of metal halide perovskites, including high carrier motilities, low recombination rates, the tunable spectral absorption range are attributed to unique electronic these materials. While DFT provides reliable structures stabilities it performs poorly in structure prediction. relativistic GW approximation has been demonstrated be able capture accurately, but at an extremely computational cost. Here we report efficient...

Scanning Kelvin probe microscopy demonstrates that water-induced charge trapping at the SiO2 dielectric – visualized in real time and space is responsible for commonly observed gate-bias-induced threshold-voltage shift organic field-effect transistors. When a bias applied to electrodes, charges are injected onto (see background of figure). contacts grounded, released again (foreground picture).

The stochastic Liouville equation is applied to the field of organic magnetoresistance perform detailed microscopic calculations on different proposed models. By adapting this equation, influence a magnetic current in bipolaron, electron-hole pair, and triplet models calculated. simplicity wide applicability makes it powerful tool for interpreting experimental results measurements semiconductors. New insights are gained hopping rates disorder magnetoresistance.

We present a scaling theory for charge transport in disordered molecular semiconductors that extends percolation by including bonds with conductances close to the percolating one random-resistor network representing hopping. A general and compact expression is given mobility Miller-Abrahams Marcus hopping on different lattices Gaussian energy disorder, parameters determined from numerically exact results. The charge-concentration dependence universal. model-specific temperature can be used...

Because of its thermal stability, lead-free composition, and nearly ideal optical electronic properties, the orthorhombic CsSnI3 perovskite is considered promising as a light absorber for all-inorganic solar cells. However, susceptibility this three-dimensional toward oxidation in air has limited development cells based on material. Here, we report findings computational study which identifies Rb y Cs1-y Sn(Br x I1-x )3 perovskites cell applications, prepared by substituting cations (Rb Cs)...

The two-dimensional (2D) mixed halide perovskite PEA2Pb(I1-x Br x )4 exhibits high phase stability under illumination as compared to the three-dimensional (3D) counterpart MAPb(I1-x )3. We explain this difference using a thermodynamic theory that considers sum of compositional and photocarrier free energy. Ab initio calculations show improved 2D is caused by preferred I-Br distribution, leading much lower critical temperature for segregation in dark than 3D perovskite. Moreover, smaller...

Ferromagnetism was recently observed at unexpectedly high temperatures in La-doped CaB6. The starting point of all theoretical proposals to explain this observation is a semimetallic electronic structure calculated for CaB6 within the local density approximation. Here we report results parameter-free quasiparticle calculations single-particle excitation spectrum which show that not semimetal but semiconductor with band gap 0.8+/-0.1 eV. Magnetism La(x)Ca1-xB6 occurs just on metallic side...

We present a theoretical description of polaron dc conductivities in organic molecular crystals. Our approach is based on rigorous evaluation the Kubo formula for electrical conductivity within mixed Holstein-Peierls model. It generalizes result Holstein's local-coupling theory by treating both local and nonlocal electron-phonon interactions nonperturbatively. The general supplemented an application to simplified model crystal order emphasize essential physics. Accompanied illustrative...

We explore the magnetoelectroluminescence (MEL) of organic light-emitting diodes by evaluating magnetic-field dependent fraction singlet excitons formed. use two- and multisite polaron-hopping models with spin mixing hyperfine fields different triplet exciton formation rates k(S) k(T). A huge MEL is predicted when in competition k(T) significantly larger than k(S). This also leads to a low-field structure that agreement recent experiments.