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Critical Role of Intermolecular-Interaction-Mediated Conformational Dynamics in Sensitized OLEDs
Cheng-Yu Yao1, Qing-Yu Meng1, Xue-Liang Wen1
1Key Lab of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing 100084, P. R. China.
The Journal of Physical Chemistry Letters
|October 1, 2025
Summary
Molecular rigidity and intermolecular interactions critically impact energy transfer efficiency in sensitized organic light-emitting diodes (OLEDs). Understanding these factors is key to developing high-performance OLEDs with improved efficiency and color purity.
Area of Science:
- Materials Science
- Organic Electronics
- Photophysics
Background:
- High Förster resonance energy transfer efficiency (ΦFRET) is crucial for sensitized organic light-emitting diodes (OLEDs) using thermally activated delayed fluorescence sensitizers.
- The energy transfer process in amorphous solid films involves complex intermolecular interactions that are not fully understood.
- Molecular structure, including rigidity and conformation, is hypothesized to influence energy transfer dynamics.
Purpose of the Study:
- To investigate the interplay of intermolecular interactions and molecular rigidity on Förster resonance energy transfer efficiency (ΦFRET) in sensitized OLEDs.
- To elucidate the underlying mechanisms responsible for variations in energy transfer rates (kFRET) and ΦFRET.
- To provide insights for designing high-performance sensitized OLED materials.
Main Methods:
- Development of a multiscale model to simulate energy transfer processes.
- Experimental verification of energy transfer rates (kFRET ~10^7 s^-1).
- Molecular-level calculations to analyze intermolecular interactions and conformational dynamics.
Main Results:
- For nonrigid DMAC-TRZ, strong intermolecular interactions induce low-energy conformers, reducing Franck-Condon factor weighted density of states (FCWD) and thus kFRET and ΦFRET.
- For rigid ACRSA, weakened intermolecular interactions and preserved conformation lead to uniform FCWD parameters, resulting in superior kFRET and ΦFRET.
- Molecular rigidity significantly influences intermolecular interactions and conformational dynamics, directly impacting energy transfer efficiency.
Conclusions:
- Intermolecular-interaction-mediated conformational dynamics play a critical role in energy transfer efficiency in sensitized OLEDs.
- Molecular rigidity is a vital factor in developing high-performance sensitized OLEDs by controlling intermolecular interactions and conformational stability.
- The study reveals a key mechanism limiting energy transfer in nonrigid sensitizers and highlights the advantage of rigid structures.
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