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Intrinsic Self-Trapped Excitons in Graphitic Carbon Nitride
Junhong Yu1, Yunhu Wang2, Yubu Zhou3
1LUMINOUS! Centre of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue 639798, Singapore.
Nano Letters
|March 18, 2024
Summary
Graphitic carbon nitride (g-C3N4) nanosheets exhibit self-trapped excitons, not independent charge carriers. Transient spectroscopy reveals ultrafast exciton trapping, impacting optoelectronics and photocatalysis research.
Area of Science:
- Materials Science
- Photochemistry
- Semiconductor Physics
Background:
- Graphitic carbon nitrides (g-C3N4) are low-cost, stable, and eco-friendly layered semiconductors.
- g-C3N4 shows promise in optoelectronics and photocatalysis.
- The behavior of photoexcited carriers in g-C3N4 remains debated, with band theory often applied.
Purpose of the Study:
- To investigate the fundamental nature of photoexcited states in g-C3N4 nanosheets.
- To clarify the role of charge carriers versus excitons in g-C3N4 photophysics.
- To provide insights for optimizing g-C3N4 in energy conversion applications.
Main Methods:
- Transient spectroscopy studies were performed on g-C3N4 nanosheets.
- Analysis included exciton trapping dynamics and polarization memory.
- Stimulated emission properties were investigated.
Main Results:
- Observed broad trapped exciton-induced absorption.
- Demonstrated picosecond exciton trapping, independent of photoexcitation density.
- Detected transient self-trapped exciton (STE)-induced stimulated emissions.
- Confirmed ultrafast exciton trapping polarization memory.
Conclusions:
- Results strongly suggest that self-trapped excitons (STEs) intrinsically define the photoexcited states in g-C3N4.
- The findings challenge the conventional independent charge-carrier picture.
- This work offers new perspectives on g-C3N4 photophysics and potential for enhanced energy conversion efficiency.
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