TY - JOUR A1 - Hahn, Tobias A1 - Tscheuschner, Steffen A1 - Saller, Christina A1 - Strohriegl, Peter A1 - Boregowda, Puttaraju A1 - Mukhopadhyay, Tushita A1 - Patil, Satish A1 - Neher, Dieter A1 - Bässler, Heinz A1 - Köhler, Anna T1 - Role of Intrinsic Photogeneration in Single Layer and Bilayer Solar Cells with C-60 and PCBM JF - The journal of physical chemistry : C, Nanomaterials and interfaces Y1 - 2016 U6 - https://doi.org/10.1021/acs.jpcc.6b08471 SN - 1932-7447 VL - 120 SP - 25083 EP - 25091 PB - American Chemical Society CY - Washington 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 - 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 - 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 - 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 - 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 - 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 - 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 - Köhler, Anna A1 - Beljonne, David T1 - The singlet-triplet exchange energy in conjugated polymers Y1 - 2004 SN - 1616-3028 SN - 1616-301X ER -