We study electrochemical p- and n-type doping in the well-known light-emitting polymer poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV). Doping reactions are characterized using cyclic voltammetry. Optical measurements including photoluminescence and UV/Vis/NIR transmission were performed on doped samples. We find that oxidation in MEH-PPV is a highly reversible reaction resu...

2210-271X/$ see front matter 2012 Elsevier B.V. http://dx.doi.org/10.1016/j.comptc.2012.05.018 ⇑ Corresponding author. Address: Computationa George Mason University, 4400 University Dr, MS 6 Fax: +1 703 993 9300. E-mail address: [email protected] (E. Blaisten-Bar A series of oligopyrrole dications, n-Py , n = 1–12, 15, 18, 21, 24, 27 are studied with hybrid density functional theory at the B3PW9...

New developments in the nascent field of organic spintronics are discussed. Two classes of phenomena can be discerned. In hybrid organic spin valves (OSVs), an organic semiconducting film is sandwiched between two ferromagnetic (FM) thin films, aiming at magnetoresistive effects as a function of the relative alignment of the respective magnetization directions. Alternatively, organic magnetores...

Much progress has been made recently in the study of the effects of electron-phonon (el-ph) coupling in doped insulators using angle resolved photoemission (ARPES), yielding evidence for the dominant role of el-ph interactions in underdoped cuprates. As these studies have been limited to doped Mott insulators, the important question arises how this compares with doped band insulators where simi...

Two quinonoid bis(dicyanomethylene) oligothiophenes, terthiophene and quaterthiophene analogues of TCNQ, have been investigated by spectroelectrochemical experiments and density functional theory calculations. Electrochemical data show that the molecules can be both reduced and oxidized at relatively low potentials, and that the quaterthiophene derivative forms four stable redox species, the di...

We have theoretically investigated the effect of doping in oligothiophenes (Tn, n=2-8) with the DFT method at UB3LYP level with 6-31G(d) basis set. Our attention focused on the study of the geometrical and electronic properties in the neutral and doped states. We show that the doping process modify both bond lengths and torsion angles and also electronic properties by enhancing the planarity an...

The Holstein Hubbard and Holstein t–J models are studied for a wide range of phonon frequencies, electron–electron and electron–phonon interaction strengths on finite lattices with up to ten sites by means of direct Lanczos diagonalization. Previously the necessary truncation of the phononic Hilbert space caused serious limitations to either very small systems (four or even two sites) or to wea...

The intrinsically conducting polymer (ICP), polyaniline (PANI) is synthesized by chemical oxidative polymerization process with the help of water soluble support polymer poly-vinyl alcohol (PVA). The field dependence of the dielectric response is measured in the frequency range 50 Hz-1 MHz and temperature range 140-318 K. The frequency dependence of the imaginary impedance (Z′′) is found to obe...

Using a variational procedure based on Lee-Low-Pines and Huybrechts canonical transformations, we study the stability region of two-dimensional bipolarons confined in a parabolic quantum dot, subject to a uniform magnetic field. In the framework of our approach, we calculate the ground-state energy for two-dimensional magnetobipolarons, together with the free polaron ground-state energy, by per...