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Maximizing Room-Temperature Red Phosphorescence in Contorted Hexabenzocoronene Derivatives
Marko R Ivancevic1, Moses D Ogbaje2, Jesse A Wisch3
1Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, United States.
Researchers achieved rare, efficient, second-scale room-temperature phosphorescence (RTP) in red light using contorted hexabenzocoronene (cHBC) molecules. Deuteration further enhanced this red RTP, extending its lifetime and efficiency in polymer composites.
Area of Science:
- Materials Science
- Organic Chemistry
- Photophysics
Background:
- Achieving long-lived room-temperature phosphorescence (RTP) in the red/near-infrared region is challenging due to nonradiative deactivation of low-energy excited states in organic molecules.
- Rare reports exist for organic molecules exhibiting second-scale RTP at room temperature, especially in the red spectrum.
Purpose of the Study:
- To investigate the potential of contorted hexabenzocoronene (cHBC) for achieving second-scale room-temperature phosphorescence (RTP) in the red/near-infrared spectrum.
- To understand the mechanisms behind efficient triplet generation and phosphorescence in cHBC-based systems.
- To explore strategies for enhancing the lifetime and efficiency of red RTP.
Main Methods:
- Experimental observation of room-temperature phosphorescence (RTP) from contorted hexabenzocoronene (cHBC) embedded in a rigid polymer matrix.
- Photophysical characterization to determine the efficiency and lifetime of RTP.
- Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT) calculations to elucidate the intersystem crossing (ISC) mechanism.
- Perdeuteration of cHBC to investigate its effect on RTP properties.
Main Results:
- Second-scale red RTP was successfully observed from cHBC embedded in a rigid polymer.
- The RTP exhibited high efficiency, with approximately 23% of steady-state photoluminescence originating from triplets.
- Perdeuteration of cHBC significantly suppressed nonradiative recombination, leading to prolonged red RTP with a lifetime exceeding 5 seconds and a steady-state phosphorescence fraction of 44%.
Conclusions:
- Contorted hexabenzocoronene (cHBC) is a promising chromophore for achieving efficient, second-scale red/near-infrared room-temperature phosphorescence (RTP).
- Efficient intersystem crossing (ISC) from the lowest singlet to a nearly resonant triplet state is proposed as the mechanism for high triplet generation efficiency.
- Perdeuteration is an effective strategy to enhance RTP lifetime and efficiency by reducing vibrational nonradiative decay pathways.
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