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Updated: Jul 5, 2025
09:00
Experimental Methods for Spin- and Angle-Resolved Photoemission Spectroscopy Combined with Polarization-Variable Laser
Published on: June 28, 2018
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Anthracene derivatives with strong spin-orbit coupling and efficient high-lying reverse intersystem crossing beyond
Ki Ju Kim1, Jaesung Kim1, Jong Tae Lim2
1Department of Information Display, Hongik University, Seoul 04066, Republic of Korea. taekyung.kim@hongik.ac.kr.
Materials Horizons
|January 15, 2024
Summary
This study synthesized a novel molecule, 2MIQ-NPA, demonstrating efficient conversion of dark triplets to light-emitting singlets via hot exciton channels and triplet-triplet fusion, achieving high exciton utilization efficiency even without El-Sayed
Area of Science:
- Organic Chemistry
- Materials Science
- Photophysics
Background:
- Materials utilizing hot exciton channels and triplet-triplet fusion (TTF) mediate high-lying reverse intersystem crossing (hRISC) are crucial for converting non-emissive triplet excitons into radiative singlet excitons.
- This process enhances exciton utilization efficiency (EUE) beyond theoretical limits, often facilitated by El-Sayed's rule for spin-forbidden transitions.
- Investigating hRISC in molecules not strictly adhering to El-Sayed's rule is essential for expanding material design strategies.
Purpose of the Study:
- To synthesize and investigate the hRISC process in an anthracene derivative, 2MIQ-NPA, which deviates from El-Sayed's rule.
- To quantitatively analyze the contributions of direct hot exciton and TTF-mediated hot exciton channels to triplet-singlet conversion.
- To evaluate the device performance of 2MIQ-NPA as an emitter in organic electronic devices.
Main Methods:
- Synthesis of 7,7-dimethyl-9-(10-(4-(naphthalen-1-yl)phenyl)anthracen-9-yl)-7H-indeno[1,2-f]quinoline (2MIQ-NPA).
- Density Functional Theory (DFT) calculations to elucidate hRISC channels.
- Transient electroluminescence measurements for quantitative analysis of exciton conversion pathways.
- Fabrication and characterization of non-doped organic electronic devices.
Main Results:
- 2MIQ-NPA exhibits a strong spin-orbit coupling matrix element (0.116 cm⁻¹) between T4 and S1 states, facilitating hRISC.
- An overall EUE of 64.3% was achieved, with contributions from a direct hot exciton channel (19.2%) and a TTF-mediated hot exciton channel (15.1%).
- The non-doped device demonstrated excellent performance with a 7.0% external quantum efficiency despite low outcoupling efficiency.
Conclusions:
- The study confirms effective triplet-to-singlet exciton conversion in 2MIQ-NPA, even when El-Sayed's rule is not followed.
- The findings highlight the potential of designing novel emitters that bypass traditional spin-selection rules for enhanced optoelectronic performance.
- 2MIQ-NPA represents a promising material for high-efficiency organic light-emitting diodes.
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