I started as PhD student in the Organic Electronics group in July 2021 and will be working on coarse grained models of OLEDs.
I completed my integrated masters degree at the University of Edinburgh in June 2021. During my masters thesis project I studied the structure of aqueous ethanol solutions using molecular dynamics simulations. This was done to explain the concentration dependence of ethanol chemical shifts observed in 1H and 13C NMR spectra of Scotch Whisky samples.
2026
Role of a trap in disordered OLED host-guest systems
A. Stankevych, N. Kinaret, A. Zhugayevych, R. Saxena, A. Vakhnin, K.-H. Lin, D. Andrienko, H. Bässler, A. Köhler, A. Kadashchuk
Phys. Rev. Appl.,
25,
044005,
2026,
[doi]
2025
Pure-blue single-layer organic light-emitting diodes based on trap-free hyperfluorescence
O. Sachnik, N. Kinaret, R. Saxena, M. Manz, W. Liu, J. T. Blaskovits, D Andrienko, J. J. Michels, P. W. M Blom, G.-J. A. H. Wetzelaer
Nature Materials,
24,
1742-1748,
2025,
[doi]
[abstract]
Blue organic light-emitting diodes based on thermally activated delayed fluorescence suffer from low stability and broad emission. Hyperfluorescence—in which the excited state created on the thermally activated delayed fluorescence emitter is transferred to a fluorescent terminal emitter with a narrow emission spectrum—is promising towards improving colour purity and stability. However direct charge trapping on the smaller-gap terminal emitter may lead to direct emissive losses inhibited charge transport and charge imbalance. Here we demonstrate single-layer pure-blue hyperfluorescent organic light-emitting diodes that are not compromised by charge trapping on the terminal emitter. We reveal that the energetic disorder of the thermally activated delayed fluorescence sensitizer allows for the presence of a terminal emitter with a smaller energy gap without affecting charge transport. Consequently the stability benefits of single-layer organic light-emitting diodes can be combined with trap-free hyperfluorescence resulting in pure-blue emission a simple device structure high quantum and power efficiencies and state-of-the-art operational stability.
2024
Predicting molecular ordering in deposited molecular films
C. Scherer, N. Kinaret, K.-H. Lin, M. N. Qaisrani, F. Post, F. May, D. Andrienko
Adv. Energy Mater.,
14,
2403124,
2024,
[doi]
[abstract]
Thin films of molecular materials are commonly employed in organic light-emitting diodes field-effect transistors and solar cells. The morphology of these organic films is shown to depend heavily on the processing used during manufacturing such as vapor co-deposition. However the prediction of processing-dependent morphologies has until now posed a significant challenge particularly in cases where self-assembly and ordering are involved. In this work a method is developed based on coarse-graining that is capable of predicting molecular ordering in vapor-deposited films of organic materials. The method is tested on an extensive database of novel and known organic semiconductors. A good agreement between the anisotropy of the refractive indices of the simulated and experimental vapor-deposited films suggests that the method is quantitative and can predict the molecular orientations in organic films at an atomistic resolution. The methodology can be readily utilized for screening materials for organic light-emitting diodes.
2023
Elimination of Charge-Carrier Trapping by Molecular Design
O. Sachnik, X. Tan, C. Haese, N. Kinaret, K.-H. Lin, D. Andrienko, R. Graf, G.-J. A. H. Wetzelaer, J. J. Michels, Paul W. M. Blom
Nature Materials,
22,
1114-1120,
2023,
[doi]
Monitoring the charge-carrier occupied density-of-states in disordered organic semiconductors under non-equilibrium conditions using thermally stimulated luminescence spectroscopy
A. Stankevych, R. Saxena, A. Vakhnin, F. May, C. Pflumm, N. Kinaret, D. Andrienko, J. Genoe, H. Baessler, A. Koehler, A. Kadashchuk
Phys. Rev. Appl.,
19,
054007,
2023,
[doi]
[abstract]
The dynamics of charge carriers in disordered organic semiconductors is inherently difficult to probe by spectroscopic methods. Thermally stimulated luminescence (TSL) is an approach that detects the luminescence resulting from the recombination of spatially-well-separated geminate charge pairs usually at low temperature. In this way the density of states (DOS) for charges can be determined. In this study we demonstrate that TSL can also be used for probing an occupied density of states formed by a low-temperature energetic relaxation of photogenerated charges. Another approach used to gain an insight into the charge-relaxation process is kinetic Monte Carlo (KMC) simulations. Here we use both techniques to determine the energetic distribution of charges at low temperatures. We find that the charge dynamics is frustrated yet this frustration can be overcome in TSL by using an infrared (IR) push pulse and in KMC simulations by a long simulation time that allows for long-range tunneling. Applying the IR-push TSL to pristine amorphous films of 18 commonly used low-molecular-weight organic light-emitting diode materials we find that the width of the occupied DOS amounts to about 2/3 of the available DOS. The same result is obtained in KMC simulations that consider spatial correlations between site energies. Without the explicit consideration of energetic correlations the experimental values cannot be reproduced which testifies to the importance of spatial correlations.
