A5056007847- X-ray Diffraction in Crystallography
- Crystallization and Solubility Studies
- Photochemistry and Electron Transfer Studies
- Organic Light-Emitting Diodes Research
- Spectroscopy and Quantum Chemical Studies
- Luminescence and Fluorescent Materials
- Organic Electronics and Photovoltaics
- Advanced Chemical Physics Studies
- X-ray Spectroscopy and Fluorescence Analysis
- Molecular Junctions and Nanostructures
- Machine Learning in Materials Science
- Electron Spin Resonance Studies
- Magnetism in coordination complexes
- Electron and X-Ray Spectroscopy Techniques
- Porphyrin and Phthalocyanine Chemistry
- Photoreceptor and optogenetics research
- ZnO doping and properties
- Synthesis and Properties of Aromatic Compounds
- Metal complexes synthesis and properties
- Metal-Catalyzed Oxygenation Mechanisms
- Molecular Sensors and Ion Detection
- Quantum Dots Synthesis And Properties
- Lanthanide and Transition Metal Complexes
- Laser-Matter Interactions and Applications
- Copper-based nanomaterials and applications
Newcastle University
2016-2025
Indian Institute of Science Bangalore
2021
University of Southampton
2021
University of St Andrews
2021
Newcastle upon Tyne Hospital
2015-2021
Paul Scherrer Institute
2011-2016
École Polytechnique Fédérale de Lausanne
2011-2015
California Institute of Technology
2015
Swiss Light Source
2011-2015
University of Birmingham
2007-2012
Abstract Knowing the underlying photophysics of thermally activated delayed fluorescence (TADF) allows proper design high efficiency organic light-emitting diodes. We have proposed a model to describe reverse intersystem crossing (rISC) in donor–acceptor charge transfer molecules, where spin–orbit coupling between singlet and triplet states is mediated by one local donor (or acceptor). This second order, vibronically coupled mechanism describes basic TADF. Through series measurements,...
Abstract Factors influencing the rate of reverse intersystem crossing ( k rISC ) in thermally activated delayed fluorescence (TADF) emitters are critical for improving efficiency and performance third‐generation heavy‐metal‐free organic light‐emitting diodes (OLEDs). However, present understanding TADF mechanism does not extend far beyond a thermal equilibrium between lowest singlet triplet states consequently research has focused almost exclusively on energy gap these two states. Herein, we...
Thermally activated delayed fluorescence (TADF) has recently emerged as one of the most attractive methods for harvesting triplet states in metal-free organic materials application light emitting diodes (OLEDs). A large number TADF molecules have been reported literature with purpose enhancing efficiency OLEDs by converting non-emissive into emissive singlet states. emitters are able to harvest both singlets and through (prompt delayed), latter due thermally reverse intersystem crossing...
The recent progress in the theory of organic molecules exhibiting thermally activated delayed fluorescence (TADF) is discussed with a particular focus upon their application highly efficient purely light emitting diodes (OLEDs).
Abstract Regio- and conformational isomerization are fundamental in chemistry, with profound effects upon physical properties, however their role excited state properties is less developed. Here two regioisomers of bis(10H-phenothiazin-10-yl)dibenzo[b,d]thiophene- S,S -dioxide, a donor–acceptor–donor (D–A–D) thermally-activated delayed fluorescence (TADF) emitter, studied. 2,8-bis(10H-phenothiazin-10-yl)dibenzo[b,d]thiophene- -dioxide exhibits only one quasi-equatorial conformer on both...
The emission of circularly polarized light is central to many applications, including data storage, optical quantum computation, biosensing, environmental monitoring, and display technologies. An emerging method induce (chiral) (CP) electroluminescence from the active layer polymer light-emitting diodes (polymer OLEDs; PLEDs) involves blending achiral polymers with chiral small-molecule additives, where handedness/sign CP controlled by absolute stereochemistry small molecule. Through...
Limitations imposed by spin statistics governing exciton formation has meant that most efficient organic light-emitting diodes (OLEDs) have relied upon complexes containing heavy metals. This can be overcome exploiting thermally activated delayed fluorescence (TADF), which opened the opportunity to design emitters composed only of lighter, more abundant elements. For these complexes, charge-transfer excitations play a central role, meaning modeling their properties within framework...
Abstract By inverting the common structural motif of thermally activated delayed fluorescence materials to a rigid donor core and multiple peripheral acceptors, reverse intersystem crossing (rISC) rates are demonstrated in an organic material that enables utilization triplet excited states at faster than Ir‐based phosphorescent materials. A combination inverted structure donor–acceptor interactions yields up 30 vibronically coupled singlet within 0.2 eV involved rISC. This gives significant...
The temperature dependent rate of a thermally activated process is given by the Arrhenius equation. exponential decrease in with activation energy, which this imposes, strongly promotes processes small barriers. This criterion one most challenging during design delayed fluorescence (TADF) emitters used organic light emitting diodes. energy usually achieved donor-acceptor charge transfer complexes. However, sacrifices radiative and therefore incommensurate high luminescence quantum yields...
Solid state solvation, crucial for understanding the device properties of 3rd generation organic light emitting diodes (OLEDs) based upon thermally activated delayed fluorescence (TADF), is investigated using molecular dynamics and quantum chemistry.
We present a static and picosecond X-ray absorption study at the Cu K-edge of bis(2,9-dimethyl-1,10-phenanthroline)copper(I) ([Cu(dmp)2](+); dmp = 2,9-dimethyl-1,10-phenanthroline) dissolved in acetonitrile dichloromethane. The steady-state photoluminescence spectra dichloromethane are also presented show shift to longer wavelengths for latter, which points stronger stabilization excited complex. fine structure features transient allow an unambiguous assignment electronic geometric molecule...
Nanostructures of transition metal oxides, such as zinc oxide, have attracted considerable interest for solar-energy conversion and photocatalysis. Both applications are sensitive to the transport trapping photoexcited charge carriers. The probing electron has recently become possible using time-resolved element-sensitive methods, X-ray spectroscopy. However, valence-band-trapped holes so far escaped observation. Herein we use absorption spectroscopy combined with a dispersive emission...
Dual luminescence (RTP and TADF) is observed in a series of donor–acceptor–donor molecules.
Abstract Titanium dioxide (TiO 2 ) is the most popular material for applications in solar‐energy conversion and photocatalysis, both of which rely on creation, transport, trapping charges (holes electrons). The nature lifetime electron traps at room temperature have so far not been elucidated. Herein, we use picosecond X‐ray absorption spectroscopy Ti K‐edge Ru L 3 ‐edge to address this issue photoexcited bare N719‐dye‐sensitized anatase amorphous TiO nanoparticles. Our results show that 100...
X-ray spectroscopy delivers strong impact across the physical and biological sciences by providing end users with highly detailed information about electronic geometric structure of matter. To decode this in challenging cases, e.g., operando catalysts, batteries, temporally evolving systems, advanced theoretical calculations are necessary. The complexity resource requirements often render these out reach for users, therefore, data not interpreted exhaustively, leaving a wealth valuable...
The development of high-brilliance third- and fourth-generation light sources such as synchrotrons X-ray free-electron lasers (XFELs), the emergence laboratory-based spectrometers, instrumental methodological advances in absorption (XAS) (non)resonant emission (XES RXES/RIXS) spectroscopies have had far-reaching effects across natural sciences. However, new kinds experiments, their ever-higher resolution data acquisition rates, brought acutely into focus challenge accurately, quickly,...
Carbene–metal–amides (CMAs) are an emerging class of photoemitters based on a linear donor–linker–acceptor arrangement. They exhibit high flexibility about the carbene–metal and metal–amide bonds, leading to conformational freedom which has strong influence their photophysical properties. Herein we report CMA complexes with (1) nearly coplanar, (2) twisted, (3) tilted, (4) tilt-twisted orientations between donor acceptor ligands illustrate preferred ground-state conformations both...
We report new, detailed, femtosecond time-resolved photoelectron spectroscopy experiments and calculations investigating the competition between ultrafast internal conversion intersystem crossing in electronically vibrationally excited benzene at onset of "channel 3". Using different probe energies to record total yield as a function pump-probe delay we are able confirm that S(1), T(1) T(2) electronic states involved state dynamics. Time-resolved measurements then allow us unravel evolution...
The ultrafast nonadiabatic dynamics of a prototypical Cu(I)–phenanthroline complex, [Cu(dmp)2]+ (dmp = 2,9-dimethyl-1,10-phenanthroline), initiated after photoexcitation into the optically bright metal-to-ligand charge-transfer (MLCT) state (S3) is investigated using quantum nuclear dynamics. In agreement with recent experimental conclusions, we find that system undergoes rapid (∼100 fs) internal conversion from S3 S2 and S1 states at or near Franck–Condon (FC) geometry. This preceded by...
The first examples of pyrazine-based gold(III) pincer complexes are reported; their intense photoemissions can be modified by protonation, N-alkylation or metal ions, without the need for altering ligand framework. Emissions shift from red (77 K) to blue (298 due thermally activated delayed fluorescence (TADF).
Quantum dynamics and a spin-vibronic Hamiltonian are used to investigate the intersystem crossing (ISC) mechanism of narrow organoboron molecular emitter, 5,9-diphenyl-5,9-diaza-13 b-boranaphtho [3,2,1-de]anthracene (DABNA-1). We find rate ISC (kISC) in good agreement with experiment which operates via second-order coupling mechanism. The nonadiabatic activating this occurs between lowest singlet (S1) state higher lying states promoting into T2 state. large S1-T1 energy gap, combined slow...