Since 2022, I have been a visiting researcher in the Andrienko group focusing on the electronic properties of organic semiconductors (CMSOS.github.io). At MPIP, we are developing novel, scalable approaches based on electronic coarse-graining, allowing for the accurate modeling of complex molecular systems including materials for solar cells and OLEDs. My broader research and education interests are described on my personal website at zhugayevych.me.
Published in the group
2026
Beyond the Single-Angle Model: Solvent-Controlled Polymorphism Reveals the Structural Origin of RISC in DMAC-TRZ
A. D. Kuimov, A. Zhugayevych, S. Bagnich, T. B. Ballaran, Y. Azuma, K. Suzuki, H. Kaji, D. Andrienko, A. Köhler, A. Kadashchuk
submitted,
2026,
[abstract]
Thermally activated delayed fluorescence (TADF) is a key mechanism underpinning high-efficiency organic light-emitting diodes (OLEDs). If the energy gap separating the lowest singlet and triplet states (ΔEST) is small thermal activation of fast reverse intersystem crossing (RISC) can cause efficient delayed fluorescence. It is commonly assumed that ΔEST and thus RISC is controlled by a single twisting angle between donor and acceptor units. Direct experimental validation of this paradigm however remains challenging because TADF emitters in amorphous matrices exhibit a distribution of intramolecular geometries. Here we use solvent-switchable crystalline polymorphs of the benchmark TADF emitter DMAC-TRZ as a structurally controlled platform to address this issue. Reversible uptake and release of toluene induce polymorphic transformations that stabilize distinct intramolecular geometries enabling fully reversible switching between low- and high-efficiency TADF regimes with nearly two orders of magnitude variation in the RISC rate. Combined experimental measurements and first-principles calculations establish a direct structure–property relationship between crystal packing intramolecular geometry ΔEST and RISC rate. The results show that the conventional single-angle description is inadequate for emitters with flexible molecular fragments. Instead RISC is governed by a multidimensional ensemble of coupled intramolecular motions that collectively modulate charge-transfer states including ΔEST and spin-orbit coupling.
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]
2023
Electronic coarse-graining of long conjugated molecules: Case study of non-fullerene acceptors
A. Zhugayevych, K.-H. Lin, D. Andrienko
J. Chem. Phys.,
159,
024107,
2023,
[doi]
[abstract]
By considering only one electronic state per molecule charge transport models of molecular solids neglect intramolecular charge transfer. This approximation excludes materials with quasi-degenerate spatially separated frontier orbitals such as non-fullerene acceptors (NFAs) and symmetric thermally activated delayed fluorescence emitters. By analyzing the electronic structure of room-temperature molecular conformers of a prototypical NFA ITIC-4F we conclude that the electron is localized on one of the two acceptor blocks with the mean intramolecular transfer integral of 120 meV which is comparable with intermolecular couplings. Therefore the minimal basis for acceptor-donor-acceptor (A-D-A) molecules consists of two molecular orbitals localized on the acceptor blocks. This basis is robust even with respect to geometry distortions in an amorphous solid in contrast to the basis of two lowest unoccupied canonical molecular orbitals withstanding only thermal fluctuations in a crystal. The charge carrier mobility can be underestimated by a factor of two when using single site approximation for A-D-A molecules in their typical crystalline packings.