TY  - JOUR
A1  - Joshi, Siddharth
A1  - Pingel, Patrick
A1  - Grigorian, Souren
A1  - Panzner, Tobias
A1  - Pietsch, Ullrich
A1  - Neher, Dieter
A1  - Forster, Michael
A1  - Scherf, Ullrich
T1  - Bimodal temperature behavior of structure and mobility in high molecular weight p3ht thin films
N2  - We report a temperature dependent crystalline structure of spin-coated thin films of high molecular weight regioregular poly(3-hexylthiophene) (P3HT) (M-n similar to 30000 g/mol) and its correlation with charge carrier mobility. These investigations show a reversible change of the crystalline structure, where the interlayer lattice spacing (100)along the alkyl side chains continuously increases up to a temperature of about 220 degrees C; in contrast, the in-plane pi-pi distance reduces with increasing temperature. These changes in structure are reversible and can be repeated several times. The temperature-induced structural properties differ for thick and thin films, pointing to a surface/interface role in stabilization of the layer morphology. In contrast to the structural changes, the carrier mobility is rather constant in the temperature range from room temperature up to 100-120 degrees C, followed by a continuous decrease. For thick layers this drop is significant and the transistor performance almost vanishes at high temperature, however, it completely recovers upon cooling back to roorn temperature. The drop of the charge carrier mobility at higher temperatures is in contrast with expectations front the structural studies, considering the increase of crystalline fraction of the polycrystalline layer. our electrical measurements Underscore that the reduction of the macroscopic mobility is mostly caused by it pronounced decrease of the intergrain transport. The thermally induced crystallization along(100) direction and the creation of numerous small crystallites at the film-substrate interface reduce the number of long polymer chain, bridging crystalline domains, which ultimately limits the macroscopic charge transport.
Y1  - 2009
UR  - http://pubs.acs.org/journal/mamobx
U6  - https://doi.org/10.1021/Ma900021w
SN  - 0024-9297
ER  - 
TY  - JOUR
A1  - Yang, Xiao Hui
A1  - Jaiser, Frank
A1  - Neher, Dieter
A1  - Lawson, PaDreyia V.
A1  - Brédas, Jean-Luc
A1  - Zojer, Egbert
A1  - Güntner, Roland
A1  - Scanduicci de Freitas, Patricia
A1  - Forster, Michael
A1  - Scherf, Ullrich
T1  - Suppression of the keto-emission in polyfluorene light-emitting diodes : Experiments and models
N2  - The spectral characteristics of polyfluorene (PF)-based light-emitting diodes (LEDs) containing a defined low concentration of either keto-defects or of the polymer poly(9.9-octylfuorene-co-benzothiadiazole) (F8BT) are preseneted. Both types of blend layers were tested in different device configurations with respect to the relative and absolute intensities of green blue emission components. It is shown that blending hole-transporting molecules into the emission layer at low concentration or incorporation of a suitable hole-transport layer reduces the green emission contribution in the electroluminescence (EL) spectrum of the PF:F8BT blend, which is similar to what is observed for the keto- containing PF layer. We conclude that the keto-defects in PF homopolymer layers mainly constitute weakly emissive electron traps, in agreement with the results of quantum-mechanical calculations
Y1  - 2004
SN  - 1616-301X
ER  -