Organic semiconductors have been extensively studied ever since the successful fabrication of organic light-emitting diodes (OLED).4 2-44 Due to their success, it is becoming increasingly important to understand the theory behind the properties of organic materials. In order to exploit all the advantages of implementing organic materials to construct devices, a detailed understanding of charge-...

The effect of charge-carrier screening on the transport properties of a neutral graphene sheet is studied by directly probing its electronic structure. We find that the Fermi velocity, Dirac point velocity, and overall distortion of the Dirac cone are renormalized due to the screening of the electron-electron interaction in an unusual way. We also observe an increase of the electron mean free p...

One-dimensional semiconductors such as nanowires and nanotubes are attractive materials for incorporation in photovoltaic devices as they potentially offer short percolation pathways to charge-collecting contacts. We report the observation of freeelectron lifetimes in TiO2 nanotubes of the order of tens of picoseconds. These lifetimes are surprisingly short compared to those determined in films...

We present a microscopic model of a charge carrier transfer under an action of a constant electric field in a complex medium. Generalizing previous theoretical approaches, we model the dynamical environment hindering the carrier motion by dynamic perco-lation, i.e., as a medium comprising particles which move randomly on a simple cubic lattice, constrained by hard-core exclusion, and may sponta...

Double perovskites, comprising two different cations, are potential nontoxic alternatives to lead halide perovskites. Here, we characterized thin films and crystals of Cs2AgBiBr6 by time-resolved microwave conductance (TRMC), which probes formation and decay of mobile charges upon pulsed irradiation. Optical excitation of films results in the formation of charges with a yield times mobility pro...

The charge transport properties of hybrid halide perovskites are investigated with a combination of density functional theory including van der Waals interaction and the Boltzmann theory for diffusive transport in the relaxation time approximation. We find the mobility of electrons to be in the range 5-10 cm(2)V(-1)s(-1) and that for holes within 1-5 cm(2)V(-1)s(-1), where the variations depend...

Charge carrier mobilities of organic semiconductors are often characterized using steady-state measurements of space charge limited diodes. These measurements assume that charge carriers are in a steady-state equilibrium. In reality, however, energetically hot carriers are introduces by photo-excitation and injection into highly energetic sites from the electrodes. These carriers perturb the eq...

The photoelectric power conversion efficiency of polymer solar cells is till now, compared to conventional inorganic solar cells, still relatively low with maximum values ranging from 7% to 8%. This essentially relates to the existence of exciton and charge carrier loss phenomena, reducing the performance of polymer solar cells significantly. In this paper we introduce a new computer simulation...

The identities of photoexcited states in thin-film Co3O4 and the ultrafast carrier relaxation dynamics of Co3O4 are investigated with oxidation-state-specific pump−probe femtosecond core level spectroscopy. A thin-film sample is excited near the 2.8 eV optical absorption peak, and the resulting spectral changes at the 58.9 eV M2,3edge of cobalt are probed in transient absorption with femtosecon...

Actually “High”? T outstanding performance of hybrid organic−inorganic perovskites (HOIPs) in photovoltaic (PV) devices is made possible by, among other things, outstanding semiconducting properties: long real charge carrier diffusion lengths, L, of up to 5 and possibly even 10 μm, as well as a lifetime τ of ∼1 μs or more in single-crystal and polycrystalline films. Top electronic transport mat...