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Caroline Murawski

Caroline Murawski
Kurt-Schwabe-Institut Meinsberg · Organophotonic Sensing

PhD

About

50
Publications
12,884
Reads
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1,612
Citations
Introduction
Caroline Murawski is junior research group leader at Kurt-Schwabe-Institut Meinsberg. She works on new applications of organic semiconductor devices, especially OLEDs, for biophotonics. Follow us on twitter @murawskilab
Additional affiliations
November 2018 - present
Kurt Schwabe Institute Meinsberg, Germany
Position
  • Group Leader
May 2015 - October 2018
University of St Andrews
Position
  • PostDoc Position
January 2011 - April 2015
Technische Universität Dresden
Position
  • PhD Student

Publications

Publications (50)
Article
Full-text available
Revealing the intricate logic of neuronal circuits and its connection to the physiopathology of living systems constitutes a fundamental question in neuroscience. Optogenetics offers the possibility to use light of specific wavelengths to study the activity of neurons with unprecedented spatiotemporal resolution. To make use of this technique at it...
Article
Full-text available
In organic light‐emitting diodes (OLEDs), horizontal orientation of the emissive transition dipole moment (TDM) can improve light outcoupling efficiency by up to 50% relative to random orientation. Therefore, there have been extensive efforts to identify drivers of horizontal orientation. The aspect ratio of the emitter molecule and the glass‐trans...
Article
Full-text available
As solid‐state light sources based on amorphous organic semiconductors, organic light‐emitting diodes (OLEDs) are widely used in modern smartphone displays and TVs. Due to the dramatic improvements in stability, efficiency, and brightness achieved over the last three decades, OLEDs have also become attractive light sources for compact and “impercep...
Article
Full-text available
Optogenetics allows light-driven, non-contact control of neural systems, but light delivery remains challenging, in particular when fine spatial control of light is required to achieve local specificity. Here, we employ organic light-emitting diodes (OLEDs) that are micropatterned into linear arrays to obtain precise optogenetic control in Drosophi...
Article
Full-text available
Despite widespread interest, ultrathin and highly flexible light-emitting devices that can be seamlessly integrated and used for flexible displays, wearables, and as bioimplants remain elusive. Organic light-emitting diodes (OLEDs) with µm-scale thickness and exceptional flexibility have been demonstrated but show insufficient stability in air and...
Article
Strong light–matter coupling leads to the formation of mixed exciton–polariton states, allowing for a rigorous manipulation of the absorption and emission of excitonic materials. Here, we demonstrate the realization of this promising concept in organic photodetectors. By hybridizing the E11 exciton of semiconducting (6,5) single-walled carbon nanot...
Article
Full-text available
Top‐emitting organic light‐emitting diodes (OLEDs) are of interest for numerous applications, in particular for displays with high fill factors. To maximize efficiency and luminance, molecular p‐doping of the hole transport layer (p‐HTL) and a highly reflective anode contact, for example, made from silver, are used. Atomic layer deposition (ALD) is...
Article
Full-text available
The accurate characterization of thin‐film light emitting diodes (LEDs)—including organic light emitting diodes (OLEDs), perovskite LEDs, and quantum dot LEDs—is crucial to the understanding of the factors that influence their efficiency and thus to the fabrication of LEDs with improved performance and stability. In addition, detailed information a...
Article
Full-text available
Invertebrates such as Drosophila melanogaster have proven to be a valuable model organism for studies of the nervous system. In order to control neuronal activity, optogenetics has evolved as a powerful technique enabling non-invasive stimulation using light. This requires light sources that can deliver patterns of light with high temporal and spat...
Preprint
Despite widespread interest, ultrathin and highly flexible light-emitting devices that can be seamlessly integrated and used for flexible displays, wearables, and as bioimplants remain elusive. Organic light-emitting diodes (OLEDs) with $\mu$m-scale thickness and exceptional flexibility have been demonstrated but show insufficient stability in air...
Article
Full-text available
Liquid crystalline materials possess great potential as emitters in organic light‐emitting diodes (OLEDs) due to their self‐assembling property, which may lead to anisotropic films and improved charge transport. Here, the key photophysical properties of the columnar liquid crystalline emitter perylene‐3,4,9,10‐tetracarboxylic tetraethyl ester (PTCT...
Article
Full-text available
Fluorescent proteins have emerged as an attractive gain material for lasers, especially for devices requiring biocompatibility. However, due to their optical properties, integration with distributed feedback (DFB) resonators is not readily achievable. Here, a DFB laser with enhanced green fluorescent protein (eGFP) as the gain material is demonstra...
Preprint
Optogenetics allows light-driven, non-contact control of neural systems, but light delivery remains challenging, in particular when fine spatial control of light is required to achieve local specificity. Here, we employ organic light-emitting diodes (OLEDs) that are micropatterned into linear arrays to obtain precise optogenetic control in Drosophi...
Article
Full-text available
Organic optoelectronic devices combine high-performance, simple fabrication and distinctive form factors. They are widely integrated in smart devices and wearables as flexible, high pixel density organic light emitting diode (OLED) displays, and may be scaled to large area by roll-to-roll printing for lightweight solar power systems. Exceptionally...
Article
We report two donor-acceptor (D-A) materials based on a cyanoanthracene acceptor paired with diphenylamine (DPAAnCN) and carbazole (CzAnCN) donor moieties. These compounds show hybrid locally excited (LE) charge-transfer (CT) excited states (HLCT), which we demonstrated through a combined photophysical and computational study. Vacuum-deposited orga...
Article
Organic light‐emitting diodes (OLEDs) can emit light over much larger areas than their inorganic counterparts, offer mechanical flexibility, and can be readily integrated on various substrates and backplanes. However, the amount of light they emit per unit area is typically lower and the required operating voltage is higher, which can be a limitati...
Conference Paper
Orientation of transition dipoles can strongly improve the outcoupling efficiency of or-ganic LEDs (OLEDs). We present two new classes of OLED emitters that may achieve horizontal alignment: columnar liquid crystals and carbon nanotubes.
Article
Full-text available
Fluorescence imaging is an indispensable tool in biology, with applications ranging from single‐cell to whole‐animal studies and with live mapping of neuronal activity currently receiving particular attention. To enable fluorescence imaging at cellular scale in freely moving animals, miniaturized microscopes and lensless imagers are developed that...
Article
Full-text available
Optogenetics, photostimulation of neural tissues rendered sensitive to light, is widely used in neuroscience to modulate the electrical excitability of neurons. For effective optical excitation of neurons, light wavelength and power density must fit with the expression levels and biophysical properties of the genetically encoded light‐sensitive ion...
Article
A series of four novel deep blue to sky blue thermally activated delayed fluorescence (TADF) emitters (2CzdOXDMe, 2CzdOXD4MeOPh, 2CzdOXDPh and 2CzdOXD4CF3Ph) have been synthesized and characterized. These oxadiazole-based emitters demonstrated bluer emission compared with reference emitter 2CzPN thanks to the weaker acceptor strength of oxadiazole...
Chapter
In the last years, organic photovoltaics have moved from a lab curiosity to a commercially viable technology. In this chapter, we consider organic photovoltaics based on oligomers (“small molecules”) which are deposited by vacuum sublimation. While the physics of the small molecule materials is in many ways very similar to those of polymer organic...
Article
4,7‐Diphenyl‐1,10‐phenanthroline (BPhen) is widely used to create the electron transport layer (ETL) in organic light‐emitting diodes (OLEDs) because of its high electron mobility and good compatibility with alkali metal n‐dopants. However, the morphology of these ETLs is easily altered by heating due to the relatively low glass transition temperat...
Article
Full-text available
The development of materials for deep blue OLEDs will be presented. A novel donor‐acceptor TADF compound comprising oxadiazole acceptor units was studied. The emission is tuned towards deep‐blue by tuning the acceptor strength, and TADF is demonstrated. Finally, the results are compared with model sky‐blue emitter 2CzPN.
Article
While organic light-emitting diodes (OLEDs) covering all colors of the visible spectrum are widespread, suitable organic emitter materials in the near-infrared (nIR) beyond 800 nm are still lacking. Here, the first OLED based on single-walled carbon nanotubes (SWCNTs) as the emitter is demonstrated. By using a multilayer stacked architecture with m...
Conference Paper
Here, we demonstrate the successful application of organic light-emitting diodes in optogenetics to control neurons in fruit fly larvae and explore their further use as a light source in fluorescence microscopy.
Article
We study thermally evaporated thin films of Ir(ppy)3 and Ir(ppy)2(acac) by means of grazing incidence X-ray diffraction (GIXRD) and grazing incidence wide-angle X-ray scattering (GIWAXS). Ir(ppy)3 and Ir(ppy)2(acac) are both widely used as phosphorescent green emitter molecules in organic light-emitting diodes (OLEDs) and it was previously found th...
Article
We review recent progress in controlling the alignment of the transition dipole moment of electroluminescent molecules to maximize the light extraction efficiency in OLEDs. Particular focus devoted to ways of measuring molecular orientation and on linking molecular structure to alignment.
Article
Full-text available
With the advent of optogenetics, numerous functions in cells have been rendered responsive to the experimental delivery of light. The most common implementation of this technique features neurons genetically modified to express light-sensitive ion channel proteins, which open specifically in response to pulses of blue light, triggering electrical i...
Article
Full-text available
Organic light emitting diodes (OLEDs) are in widespread use in today’s mobile phones and are likely to drive the next generation of large area displays and solid-state lighting. Here we show steps towards their utility as a platform technology for biophotonics, by demonstrating devices capable of optically controlling behaviour in live animals. Usi...
Conference Paper
Thin films of the phosphorescent emitters Ir(ppy)3 and Ir(ppy)2(acac) are investigated by GIXRD and GIWAXS. Both molecules form crystalline grains and exhibit a preferred orientation that is pertained even when doped into a host.
Conference Paper
Optogenetics is an emerging method in biology that enables controlling neurons with light. We use organic light-emitting diodes to stimulate neurons in Drosophila larvae and investigate subsequent behavioral changes at different light intensities.
Article
Full-text available
The orientation of the emissive dipole moment of seven iridium-based phosphorescent emitter molecules commonly used in organic light-emitting diodes (OLEDs) is investigated. The orientation of Ir(ppy)3, Ir(ppy)2(acac), Ir(chpy)3, Ir(dhfpy)2(acac), Ir(BT)2(acac), Ir(MDQ)2(acac), and Ir(piq)3 is determined by measuring the angle dependent spectral ra...
Article
Full-text available
We investigate the properties of N,N′-[(Diphenyl-N,N′-bis)9,9,-dimethyl-fluoren-2-yl]-benzidine (BF-DPB) as hole transport material (HTL) in organic light-emitting diodes (OLEDs) and compare BF-DPB to the commonly used HTLs N,N,N′,N′-tetrakis(4-methoxyphenyl)-benzidine (MeO-TPD), 2,2′,7,7′-tetrakis(N,N′-di-p-methylphenylamino)-9,9′-spirobifluorene...
Article
Triplet harvesting in organic light-emitting diodes (OLEDs) from a blue fluorescent to a green phosphorescent emitter is important for the development of highly efficient white OLEDs for lighting applications. Here, we report new blue fluorescent bulk emitters with high triplet energies for triplet harvesting in OLEDs. Based on the chemical structu...
Article
This article describes the first systematic investigation of how the efficiency roll-off in organic light-emitting diodes (OLEDs) is influenced by the position and orientation of the emitter molecules within the OLED cavity. The efficiency roll-off is investigated for two OLED stacks containing either the phosphorescent emitter Ir(MDQ)2(acac) or Ir...
Article
Organic light-emitting diodes (OLEDs) have attracted much attention in research and industry thanks to their capability to emit light with high efficiency and to deliver high-quality white light that provides good color rendering. OLEDs feature homogeneous large area emission and can be produced on flexible substrates. In terms of efficiency, OLEDs...
Article
We report on the development and detailed investigation of highly efficient p–i–n phosphorescent organic light-emitting diodes (PhOLEDs) using 4,4′-bis(carbazol-9-yl)-biphenyl (CBP) as a single organic semiconductor matrix. Following optimization of doping concentration of both the phosphorescent emitter molecule and of the p- and n-type dopants, a...
Article
Full-text available
We investigate the average orientation of the transition dipole moments of two green phosphorescent emitters Ir(ppy)3 and Ir(ppy)2(acac) embedded in a CBP matrix, using in-situ angle resolved electroluminescence spectroscopy and optical simulations. The dipole orientation of Ir(ppy)3 is nearly isotropic while 77% of the dipoles are horizontally ali...
Conference Paper
Excessive charge carrier densities in the emission layer of organic light-emitting diodes (OLEDs) can lead to significant quenching by triplet-polaron-annihilation [1] or field-induced quenching [2]. Thus, to increase the efficiency of OLEDs further, a technique for the reliable determination of charge carrier densities in OLEDs is most desirable....
Article
Full-text available
Organic light-emitting diodes (OLEDs) using the red phosphorescent emitter iridium(III)bis(2-methyldibenzo[f,h]quinoxaline) (acetylacetonate) [Ir(MDQ)2(acac)] are studied by time-resolved electroluminescence measurements. A transient overshoot after voltage turn-off is found, which is attributed to electron accumulation on Ir(MDQ)2(acac) molecules....
Article
Full-text available
Exciton generation and transfer processes in a multilayer organic light-emitting diode (OLED) are studied in order to realize OLEDs with warm white color coordinates and high color-rendering index (CRI). We investigate a host-guest-system containing four phosphorescent emitters and two matrix materials with different transport properties. We show,...
Conference Paper
Full-text available
The effect of the electron blocking layer on the performance of white organic light-emitting diodes is studied. A variation of the material influences not only the carrier transport, but also the light distribution from the different emitters. Highest external quantum efficiency is reached for the material with the worst electrical properties, whil...

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