Christian J. Mueller
University of Bayreuth
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Publication
Featured researches published by Christian J. Mueller.
Journal of Materials Chemistry | 2016
Chao Wang; Christian J. Mueller; Eliot Gann; Amelia C. Y. Liu; Mukundan Thelakkat; Christopher R. McNeill
The photovoltaic properties of a series of diketopyrrolo[3,4-c]pyrrole (DPP) copolymers containing 3,4-ethylenedioxythiophene (EDOT) as a comonomer are reported. With use of different aryl flanking units on the DPP core, namely thiophene, pyridine or phenyl, optical gaps ranging from 1.91 eV to 1.13 eV are achieved. When blended with the fullerene derivative [6,6]-phenyl C71-butyric acid methyl ester (PC71BM), the thiophene-flanked copolymer PDPP[T]2-EDOT with an optical gap of 1.13 eV was found to have the best photovoltaic performance, with an efficiency of 2.5% in an inverted device architecture. Despite having the lowest open circuit voltage of the three polymers studied, PDPP[T]2-EDOT-based devices were able to achieve superior efficiencies due to the high short circuit current of up to ∼15 mA cm−2. PDPP[T]2-EDOT-based devices also exhibit higher external quantum efficiencies which are associated with a superior microstructure – as revealed by transmission electron microscopy (TEM) and grazing incidence wide-angle X-ray scattering (GIWAXS) – which is associated with the enhanced aggregation tendency of PDPP[T]2-EDOT chains. In particular PDPP[T]2-EDOT : PC71BM blends were found to have a finer phase separated morphology with superior thin-film crystallinity. Surface morphology was also investigated with atomic force microscopy and near-edge X-ray absorption fine-structure spectroscopy.
Journal of Materials Chemistry C | 2015
Christian J. Mueller; Eliot Gann; Christopher R. McNeill; Mukundan Thelakkat
A series of π-extended polydiketopyrrolo[3,4-c]pyrroles with a varying degree of fluorination on the thiophene–phenyl–thiophene comonomer was synthesized by Stille polycondensation. The influence of the degree of fluorination was studied with regard to the polymer properties, such as absorption, electrochemical redox potentials, the solid state structure as well as depth-dependent molecular alignment in thin films. Additionally, their performance in organic field effect transistors was evaluated. Whereas fluorination slightly increases the alkyl lamella and shrinks the π–π spacings, the coherence lengths were found to improve significantly in both directions. All polymers were found to be p-type materials when employed in organic field effect transistors (OFET). These devices can be tuned towards ambipolarity in the case of the tetrafluorinated copolymer upon thermal annealing.
Journal of Materials Chemistry C | 2017
Tina Weller; M. Breunig; Christian J. Mueller; Eliot Gann; Christopher R. McNeill; Mukundan Thelakkat
A series of copolymers based on thieno[3,4-c]pyrrole-4,6-dione and thiophene-phenyl-thiophene with varying degrees of fluorination on the phenyl unit was synthesized by Stille polycondensation. The influence of the degree of fluorination on the optical, thermal and electrochemical properties of these polymers is systematically studied. Additionally, the charge transport in organic field effect transistors (OFETs) as well as the thin film alignment are investigated. After thermal annealing the non-fluorinated as well as difluorinated polymers show ambipolar charge transport in OFETs. In contrast, tetrafluorination results in exclusively n-type behaviour with an electron mobility of 3.7 × 10−4 cm2 V−1 s−1. GIWAXS measurements of as-cast and annealed films reveal a very interesting structural alignment in thin films. All polymers show the rarely observed “end-on” orientation, where the polymer chains stand on the substrate. This may be explained by the low molecular weights of these polymers in relation to the film thickness. Fluorination does not influence the microstructural properties, only the propensity of crystallization is increased.
Macromolecules | 2010
Amy M. Ballantyne; Toby A. M. Ferenczi; Mariano Campoy-Quiles; Tracey M. Clarke; Andrea Maurano; Kien Hon Wong; Weimin Zhang; Natalie Stingelin-Stutzmann; Ji-Seon Kim; Donal D. C. Bradley; James R. Durrant; Iain McCulloch; Martin Heeney; Jenny Nelson; Steve Tierney; Warren Duffy; Christian J. Mueller; Paul Smith
Advanced Functional Materials | 2015
Christian J. Mueller; Chetan R. Singh; Martina Fried; Sven Huettner; Mukundan Thelakkat
Chemistry of Materials | 2016
Christian J. Mueller; Eliot Gann; Chetan R. Singh; Mukundan Thelakkat; Christopher R. McNeill
Advanced Energy Materials | 2015
Christian J. Mueller; Michael Brendel; Pia Ruckdeschel; Jens Pflaum; Mukundan Thelakkat
Journal of Polymer Science Part B | 2016
Christian J. Mueller; Chetan R. Singh; Mukundan Thelakkat
Macromolecules | 2016
Christian J. Mueller; Tobias Klein; Eliot Gann; Christopher R. McNeill; Mukundan Thelakkat
Advanced Materials Interfaces | 2016
Chetan R. Singh; Cheng Li; Christian J. Mueller; Sven Hüttner; Mukundan Thelakkat