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  - Wilson, J. S.
A1  - Chawdhury, Nazia
A1  - Al-Mandhary, Muna R. A.
A1  - Younus, M.
A1  - Khan, Muhammad S.
A1  - Raithby, Paul R.
A1  - Friend, Richard H.
T1  - The energy gap law for triplet States in Pt-containing conjugated polymers and monomers
Y1  - 2001
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  - 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  - 
TY  - JOUR
A1  - Devi, Lekshmi Sudha
A1  - Al-Suti, Mohammed K.
A1  - Dosche, Carsten
A1  - Khan, Muhammad S.
A1  - Friend, Richard H.
A1  - Köhler, Anna
T1  - Triplet energy transfer in conjugated polymers : I. Experimental investigation of a weakly disordered compound
N2  - Efficient triplet exciton emission has allowed improved operation of organic light-emitting diodes (LEDs). To enhance the device performance, it is necessary to understand what governs the motion of triplet excitons through the organic semiconductor. Here, we have investigated triplet diffusion using a model compound that has weak energetic disorder. The Dexter-type triplet energy transfer is found to be thermally activated down to a transition temperature T- T, below which the transfer rate is only weakly temperature dependent. We show that above the transition temperature, Dexter energy transfer can be described within the framework of Marcus theory. We suggest that below T-T, the nature of the transfer changes from phonon-assisted hopping to quantum-mechanical tunneling. The lower electron-phonon coupling and higher electronic coupling in the polymer compared to the monomer results in an enhanced triplet diffusion rate.
Y1  - 2008
ER  -