Search Results - (Author, Cooperation:F. Wudl)
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1Latest Papers from Table of Contents or Articles in PressL. Dou ; Y. Zheng ; X. Shen ; G. Wu ; K. Fields ; W. C. Hsu ; H. Zhou ; Y. Yang ; F. Wudl
American Association for the Advancement of Science (AAAS)
Published 2014Staff ViewPublication Date: 2014-01-18Publisher: American Association for the Advancement of Science (AAAS)Print ISSN: 0036-8075Electronic ISSN: 1095-9203Topics: BiologyChemistry and PharmacologyComputer ScienceMedicineNatural Sciences in GeneralPhysicsPublished by: -
2Articles: DFG German National LicensesToussaint, J. M. ; Wudl, F. ; Brédas, J. L.
College Park, Md. : American Institute of Physics (AIP)
Published 1989Staff ViewISSN: 1089-7690Source: AIP Digital ArchiveTopics: PhysicsChemistry and PharmacologyNotes: Geometry optimizations and band structure calculations are reported on two polymeric vinylene derivatives of pyrene: poly(1,6-pyrenylene vinylene) and poly(2,7-pyrenylene vinylene). The results are indicative of a dramatic sensitivity of the electronic structure on the mode of connection of the two vinylene units to the pyrene rings, in agreement with the chemist's intuition. An analysis of the atomic π orbital contributions to the one-electron wave functions shows that the HOMO–LUMO characteristics of both compounds are markedly different. The 1-6 mode of connection leads to an electronic structure similar to that of polyparaphenylene with a bandgap of 2.9 eV. The 2-7 mode of connection results in a significantly lower bandgap, around 1.7 eV, due to the stabilization of quinoid resonance structures.Type of Medium: Electronic ResourceURL: -
3Articles: DFG German National LicensesLazzaroni, R. ; Riga, J. ; Verbist, J. ; Brédas, J. L. ; Wudl, F.
College Park, Md. : American Institute of Physics (AIP)
Published 1988Staff ViewISSN: 1089-7690Source: AIP Digital ArchiveTopics: PhysicsChemistry and PharmacologyNotes: We investigate the electronic structure of polyisothianaphthene, comparing the experimental data obtained by x-ray photoelectron spectroscopy (XPS) with the results of valence effective Hamiltonian calculations. In the neutral form, the theoretical density of valence states is in very good agreement with the experimental measurements. The shifts observed for the core and valence levels upon doping confirm the very low value of the band gap in this system. Several models explaining the evolution of the line shapes in the oxidized polymer are discussed.Type of Medium: Electronic ResourceURL: -
4Articles: DFG German National LicensesPakbaz, K. ; Wu, R. ; Wudl, F. ; Heeger, A. J.
College Park, Md. : American Institute of Physics (AIP)
Published 1993Staff ViewISSN: 1089-7690Source: AIP Digital ArchiveTopics: PhysicsChemistry and PharmacologyNotes: We report the results of initial measurements on two derivatives of poly(1,6-heptadiyne): a di-ketone (PHDK) and a di-ester (PHDE). Both polymers have the degenerate ground state of poly(1,6-heptadiyne); both are soluble in common organic solvents. Electron spin resonance (ESR) measurements on pristine samples place an upper limit of 10−4 spins per monomer for both polymers. At low doping levels, we observe a single doping-induced absorption band at an energy of approximately half the π−π* gap, Eg/2; the doping-induced spectral features were fully reversible. In situ ESR and absorption measurements during doping show that charge is stored predominantly in spinless charge carriers. Because of the inequivalent carbons on the conjugated backbone, the results are discussed in terms of the (A=B)n polymer. Both PHDK and PHDE are relatively stable in air; the strength of the π−π* absorption band is nearly constant over a period of a week in air, decreasing to 80% of the initial value.Type of Medium: Electronic ResourceURL: -
5Articles: DFG German National LicensesMcElvain, J. ; Keshavarz, M. ; Wang, H. ; Wudl, F. ; Heeger, A. J.
[S.l.] : American Institute of Physics (AIP)
Published 1997Staff ViewISSN: 1089-7550Source: AIP Digital ArchiveTopics: PhysicsNotes: We report the fabrication of polymer grid triodes (PGTs) using C60 as the semiconducting medium. The structure, a self-assembling porous conducting polyaniline network placed between two semiconducting layers of C60, and sandwiched between two metal electrodes, demonstrates the I–V characteristics of a three terminal device in which the current is controlled by the grid potential. As a result of the higher mobilities of the fullerenes compared to those of conjugated polymers, the fullerene devices offer some performance advantages; the operating voltages are less than 5 V with current densities exceeding 1 mA/cm2. By fabricating devices with different grid densities, it is shown that the grid exhibits a strong influence on the I–V characteristics for high grid densities, and a correspondingly low influence for low densities, in agreement with theory. The I–V characteristics of the C60 PGTs are well described by an effective diode model, similar to that used for vacuum triodes. © 1997 American Institute of Physics.Type of Medium: Electronic ResourceURL: -
6Articles: DFG German National LicensesCha, M. ; Sariciftci, N. S. ; Heeger, A. J. ; Hummelen, J. C. ; Wudl, F.
Woodbury, NY : American Institute of Physics (AIP)
Published 1995Staff ViewISSN: 1077-3118Source: AIP Digital ArchiveTopics: PhysicsNotes: Nonlinear optical absorption in solid films of poly(3-octylthiophene) (P3OT) sensitized with methanofullerene was investigated for wavelengths from 620 to 960 nm. The nonlinear absorption is enhanced over that in either of the component materials by more than two orders of magnitude at 760 nm. The large nonlinearity results from efficient photoinduced intermolecular charge transfer from P3OT to methanofullerene, followed by absorption in the charge separated excited state. P3OT/fullerene films are promising as optical limiters; the transmission clamps at an average fluence of approximately 0.1 J/cm2. The damage threshold was 15 μJ/pulse (≈1 J/cm2 in average fluence), above which there is a permanent change in the linear transmission. © 1995 American Institute of Physics.Type of Medium: Electronic ResourceURL: -
7Articles: DFG German National LicensesSariciftci, N. S. ; Braun, D. ; Zhang, C. ; Srdanov, V. I. ; Heeger, A. J. ; Stucky, G. ; Wudl, F.
Woodbury, NY : American Institute of Physics (AIP)
Published 1993Staff ViewISSN: 1077-3118Source: AIP Digital ArchiveTopics: PhysicsNotes: The characterization of rectifying heterojunctions (diodes) fabricated from a semiconducting polymer, a soluble derivative of poly(phenylene-vinylene), and buckminsterfullerene, C60, are reported. Rectification ratios in the current versus voltage characteristics exceed 104. When illuminated, the devices exhibit a large photoresponse as a result of photoinduced electron transfer across the heterojunction interface from the semiconducting polymer (donor) onto C60 (acceptor). The photodiode and photovoltaic responses are characterized. Photoinduced electron transfer across the donor-accepted rectifying heterojunction offers potential for photodetector and for solar cell applications.Type of Medium: Electronic ResourceURL: -
8Articles: DFG German National LicensesKraabel, B. ; Hummelen, Jan C. ; Vacar, D. ; Moses, D. ; Sariciftci, N. S. ; Heeger, A. J. ; Wudl, F.
College Park, Md. : American Institute of Physics (AIP)
Published 1996Staff ViewISSN: 1089-7690Source: AIP Digital ArchiveTopics: PhysicsChemistry and PharmacologyNotes: We report time-resolved excited state absorption measurements which demonstrate subpicosecond photoinduced electron transfer using soluble derivatives of poly(p-phenylene vinylene) as donors blended with a functionalized fullerene (methanofullerene) as acceptor. The subpicosecond photoinduced absorption spectra of the polymer/methanofullerene blends show that electron transfer from the donor to the acceptor occurs within a picosecond of photoexcitation of the conjugated polymer. Precise determination of the electron transfer dynamics was obtained by monitoring the dichroic ratio. The charge separated state is metastable and persists into the millisecond time domain, yielding an asymmetry of 10 orders of magnitude between the forward and reverse electron transfer times. The increased miscibility of the functionalized methanofullerene with the conjugated polymer is important for preparation of films with sufficiently high acceptor concentrations for practical devices based on photoinduced charge separation. © 1996 American Institute of Physics.Type of Medium: Electronic ResourceURL: -
9Articles: DFG German National LicensesBrédas, J. L. ; Heeger, A. J. ; Wudl, F.
College Park, Md. : American Institute of Physics (AIP)
Published 1986Staff ViewISSN: 1089-7690Source: AIP Digital ArchiveTopics: PhysicsChemistry and PharmacologyNotes: We present valence effective Hamiltonian (VEH) band-structure calculations on polyisothianaphthene and some of its simple derivatives. Our goal is to rationalize the lowering of the band gap by about 1 eV which is experimentally observed in polyisothianaphthene (Eg=∼1 eV) relative to the parent polymer, polythiophene (Eg=∼2 eV). We show that the smaller band gap found in polyisothianaphthene can be understood on the basis of a relationship which can be established between the band gap energy and the importance of the effective quinoid contributions to the electronic structure. Our theoretical results also indicate that simple dimethyl, dimethoxy, or dicyano substitutions are not expected to affect the size of the band gap in any significant way.Type of Medium: Electronic ResourceURL: -
10Articles: DFG German National LicensesKobayashi, M. ; Colaneri, N. ; Boysel, M. ; Wudl, F. ; Heeger, A. J.
College Park, Md. : American Institute of Physics (AIP)
Published 1985Staff ViewISSN: 1089-7690Source: AIP Digital ArchiveTopics: PhysicsChemistry and PharmacologyNotes: The physical and electronic properties of poly(isothianaphthene) PITN, are reported, including initial characterization, electrochemical cyclic voltammetry, spectroscopy, and transport properties. PITN has the smallest energy gap of any known conjugated organic polymer, Eg(approximately-equal-to)1 eV. This novel conjugated polymer exhibits reversible chemical and electrochemical p-type doping with an associated high contrast color change. After doping, thin films of PITN have very low optical density in the visible portion of the spectrum. Thus, PITN is the first example of a transparent highly conducting polymer (σ∼50 Ω−1 cm−1).Type of Medium: Electronic ResourceURL: -
11Articles: DFG German National LicensesKobayashi, M. ; Colaneri, N. ; Boysel, M. ; Wudl, F. ; Heeger, A. J.
College Park, Md. : American Institute of Physics (AIP)
Published 1985Staff ViewISSN: 1089-7690Source: AIP Digital ArchiveTopics: PhysicsChemistry and PharmacologyType of Medium: Electronic ResourceURL: -
12Articles: DFG German National LicensesStaff View
ISSN: 0022-3697Keywords: Organic ferromagnetism ; buckminsterfullerene C"6"0 ; itinerant ferromagnet ; organic charge transfer solid ; soft ferromagnetSource: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002Topics: Chemistry and PharmacologyPhysicsType of Medium: Electronic ResourceURL: -
13Articles: DFG German National LicensesStaff View
ISSN: 0022-3697Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002Topics: Chemistry and PharmacologyPhysicsType of Medium: Electronic ResourceURL: -
14Articles: DFG German National LicensesStaff View
ISSN: 0038-1098Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002Topics: PhysicsType of Medium: Electronic ResourceURL: -
15Articles: DFG German National LicensesWalsh, W.M. ; Rupp, L.W. ; Wudl, F. ; Kaplan, M.L. ; Schafer, D.E. ; Thomas, G.A. ; Gemmer, R.
Amsterdam : ElsevierStaff ViewISSN: 0038-1098Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002Topics: PhysicsType of Medium: Electronic ResourceURL: -
16Articles: DFG German National LicensesSparn, G. ; Thompson, J.D. ; Allemand, P.-M. ; Li, Q. ; Wudl, F. ; Holczer, K. ; Stephens, P.W.
Amsterdam : ElsevierStaff ViewISSN: 0038-1098Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002Topics: PhysicsType of Medium: Electronic ResourceURL: -
17Articles: DFG German National LicensesStaff View
ISSN: 0038-1098Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002Topics: PhysicsType of Medium: Electronic ResourceURL: -
18Articles: DFG German National LicensesCox, S. ; Boysel, R.M. ; Moses, D. ; Wudl, F. ; Chen, J. ; Ochsenbein, S. ; Heeger, A.J. ; Walsh, W.M. ; Rupp, L.W.
Amsterdam : ElsevierStaff ViewISSN: 0038-1098Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002Topics: PhysicsType of Medium: Electronic ResourceURL: -
19Articles: DFG German National LicensesStaff View
ISSN: 0022-328XSource: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002Topics: Chemistry and PharmacologyType of Medium: Electronic ResourceURL: -
20Articles: DFG German National LicensesStaff View
ISSN: 0022-328XSource: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002Topics: Chemistry and PharmacologyType of Medium: Electronic ResourceURL: