TY  - JOUR
A1  - Zhang, Ning
A1  - Hayer, Anna
A1  - Al-Suti, Mohammed K.
A1  - Al-Belushi, Rayya A.
A1  - Khan, Muhammad S.
A1  - Köhler, Anna
T1  - The effect of delocalization on the exchange energy in meta- and para-linked Pt-containing carbazole polymers and monomers
N2  - A series of novel platinum-containing carbazole monomers and polymers was synthesized and fully characterized by UV-VIS absorption, luminescence, and photoinduced absorption studies. In these compounds, a carbazole unit is incorporated into the main chain via either a para- or a meta-linkage. We discuss the effects of linkage and polymerization on the energy levels of S-1, T-1, and T-n. The S-1-T-1 splitting observed for the meta-linked monomer (0.4 eV) is only half of that in the para-linked monomer (0.8 eV). Upon polymerization, the exchange energy in the para- linked compound reduces, yet still remains larger than in the meta-linked polymer. We attribute the difference in exchange energy to the difference in wave function overlap between electron and hole in these compounds. (c) 2006 American Institute of Physics
Y1  - 2006
UR  - http://scitation.aip.org/getpdf/servlet/ GetPDFServlet?filetype=pdf&id=JCPSA6000124000024244701000001&idtype=cvips&doi=10.1063/1.2200351&prog=normal
U6  - https://doi.org/10.1063/1.2200351
ER  - 
TY  - JOUR
A1  - Yang, C.
A1  - Vardeny, Z. V.
A1  - Köhler, Anna
A1  - Wohlgenannt, M.
A1  - Al-Suti, Mohammed K.
A1  - Khan, Muhammad S.
T1  - Spectroscopic study of spin-dependent exciton formation rates in pi-conjugated semiconductors : Comparison with electroluminescence techniques
N2  - It has been found in recent measurements that the singlet-to-triplet exciton ratio in organic light-emitting diodes (OLEDs) is larger than expected from spin degeneracy, and that singlet excitons form at a larger rate than triplets. We employed the technique of optically detected magnetic resonance to measure the spin-dependent exciton formation rates in films of a polymer and corresponding monomer, and explore the relation between the formation rates and the actual singlet-to-triplet ratio measured previously in OLEDs. We found that the spin-dependent exciton formation rates can indeed quantitatively explain the observed exciton yields, and that singlet formation rates and yields are significantly enhanced only in polymer OLEDs, but not in OLEDs made from the corresponding monomer
Y1  - 2004
ER  - 
TY  - JOUR
A1  - Sandee, A. J.
A1  - Williams, Charlotte K.
A1  - Evans, N. R.
A1  - Davies, J. E.
A1  - Boothby, C. E.
A1  - Köhler, Anna
A1  - Friend, Richard H.
A1  - Holmes, Andrew B.
T1  - Solution-processible conjugated electrophosphorescent polymers
Y1  - 2004
ER  - 
TY  - JOUR
A1  - Parkinson, P.
A1  - Aharon, E.
A1  - Chang, M. H.
A1  - Dosche, Carsten
A1  - Frey, G. L.
A1  - Köhler, Anna
A1  - Herz, L. M.
T1  - Dimensionality-dependent energy transfer in polymer-intercalated SnS2 nanocomposites
N2  - We have investigated the influence of dimensionality on the excitation-transfer dynamics in a conjugated polymer blend. Using time-resolved photoluminescence spectroscopy, we have measured the transfer transients for both a three-dimensional blend film and for quasi-two-dimensional monolayers formed through intercalation of the polymer blend between the crystal planes of an inorganic SnS2 matrix. We compare the experimental data with a simple, dimensionality- dependent model based on electronic coupling between electronic transition moments taken to be point dipoles. Within this approximation, the energy-transfer dynamics is found to adopt a three-dimensional character in the solid film and a two-dimensional nature in the monolayers present in the SnS2-polymer nanocomposite.
Y1  - 2007
UR  - http://prb.aps.org/toc/PRB/v75/i16
U6  - https://doi.org/10.1103/Physrevb.75.165206
ER  - 
TY  - JOUR
A1  - Mermer, Ö.
A1  - Veeraraghavan, G.
A1  - Francis, T. L.
A1  - Sheng, Y.
A1  - Nguyen, D. T.
A1  - Wohlgenannt, M.
A1  - Köhler, Anna
A1  - Al-Suti, Mohammed K.
T1  - Large magnetoresistance in nonmagnetic pi-conjugated semiconductor thin film devices
N2  - Following the recent observation of large magnetoresistance at room temperature in polyfluorene sandwich devices, we have performed a comprehensive magnetoresistance study on a set of organic semiconductor sandwich devices made from different pi-conjugated polymers and small molecules. The study includes a range of materials that show greatly different chemical structure, mobility, and spin-orbit coupling strength. We study both hole and electron transporters at temperatures ranging from 10 K to 300 K. We observe large negative or positive magnetoresistance (up to 10% at 300 K and 10 mT) depending on material and device operating conditions. We discuss our results in the framework of known magnetoresistance mechanisms and find that none of the existing models can explain our results.
Y1  - 2005
ER  - 
TY  - JOUR
A1  - Mak, Chris S. K.
A1  - Hayer, Anna
A1  - Pascu, S. I.
A1  - Watkins, Scott E.
A1  - Holmes, Andrew B.
A1  - Köhler, Anna
A1  - Friend, Richard H.
T1  - Blue-to-green electrophosphorescence of iridium-based cyclometallated materials.
Y1  - 2005
UR  - http://www.rsc.org/ej/CC/2005/b508695g.pdf
U6  - https://doi.org/10.1039/b508695gb70
SN  - 0022-4936
ER  - 
TY  - JOUR
A1  - Köhler, Anna
A1  - Beljonne, David
T1  - The singlet-triplet exchange energy in conjugated polymers
Y1  - 2004
SN  - 1616-3028
SN  - 1616-301X
ER  - 
TY  - JOUR
A1  - Khan, Muhammad S.
A1  - Al-Mandhary, Muna R. A.
A1  - Al-Suti, Mohammed K.
A1  - Al-Battashi, Fathiya R.
A1  - Al-Saadi, Sultan
A1  - Bjernemose, Jens K.
A1  - Mahon, Mary F.
A1  - Chawdhury, Nazia
A1  - Yonus, Muhammad
A1  - Köhler, Anna
A1  - Teat, Simon J.
A1  - Marseglia, Elizabeth A.
A1  - Tedesco, Emilio
A1  - Feeder, Neil
A1  - Ahrens, Birte
A1  - Raithby, Paul R.
T1  - Synthesis, characterisation and optical spectroscopy of platinum(II) di-ynes and poly-ynes incorporating condensed aromatic spacers in the backbone
Y1  - 2004
U6  - https://doi.org/10.1039/B405070C
SN  - 1477-9226
ER  - 
TY  - JOUR
A1  - Khan, Amena L. T.
A1  - Sreearunothai, Paiboon
A1  - Herz, Laura M.
A1  - Banach, Michael J.
A1  - Köhler, Anna
T1  - Morphology-dependent energy transfer within polyfluorene thin films
Y1  - 2004
ER  - 
TY  - JOUR
A1  - Hayer, Anna
A1  - Köhler, Anna
A1  - Arisi, E.
A1  - Bergenti, I.
A1  - Dediu, A.
A1  - Taliani, C.
A1  - Al-Suti, Mohammed K.
A1  - Khan, Muhammad S.
T1  - Polymer light-emitting diodes with spin-polarised charge injection.
Y1  - 2004
SN  - 0379-6779
ER  -