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Above 100% Efficiency Photocharge Generation in Monolayer Semiconductors by Singlet Fission Sensitization
Lei Ye1,2, Yujie Zhao3, Rong Xu4
1Key Laboratory of Excited-State Materials of Zhejiang Province, Department of Chemistry, Zhejiang University, Hangzhou 310058, China.
Journal of the American Chemical Society
|November 23, 2023
Summary
Singlet fission (SF) materials boost semiconductor efficiency by creating two excitons per photon. This study reveals optimal charge transfer in organic/2D heterostructures, achieving 126% photocharge generation efficiency.
Area of Science:
- Materials Science
- Photovoltaics
- Organic Electronics
Background:
- Singlet fission (SF) materials can enhance light-to-electricity conversion by generating two excitons from one photon.
- Two-dimensional (2D) semiconductors offer excellent charge transport but suffer from limited light absorption.
- Efficiently harvesting triplet excitons from SF at organic/inorganic interfaces remains a significant challenge.
Purpose of the Study:
- Investigate SF sensitization in organic/2D bilayer heterostructures.
- Elucidate the interplay between SF, exciton dissociation, and charge transfer.
- Optimize heterostructure design for enhanced photocharge generation.
Main Methods:
- Fabrication of high-quality organic/2D bilayer heterostructures using TIPS-Pc single crystals.
- Transient magneto-optical spectroscopy to probe ultrafast dynamics.
- Analysis of competing processes: singlet exciton fission, dissociation, and triplet exciton transport.
Main Results:
- Demonstrated ultrafast SF in sub-100 fs.
- Identified competing singlet exciton dissociation at the interface before fission.
- Observed diffusion-limited charge transfer of triplet excitons in the picosecond to nanosecond timescale.
- Achieved a remarkable photocharge generation efficiency of 126% in optimally designed heterostructures.
Conclusions:
- The competitive interplay between singlet fission, dissociation, and triplet exciton transport governs SF sensitization efficiency.
- Optimized organic/2D heterostructures offer a promising route to surpass conventional efficiency limits in 2D optoelectronics.
- This work provides critical insights into harnessing triplet excitons for advanced photovoltaic applications.
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