High-yield visible-to-ultraviolet upconversion by ZnSe quantum dots with dynamic triplet transfer
Xin Zhang1, Rongxin Zhang2, Lei Wang2
1Hubei Key Laboratory of Low Dimensional Optoelectronic Materials and Devices, Hubei University of Arts and Science, Xiangyang, China. xinzhang@hbuas.edu.cn.
Nature Communications
|July 17, 2026
Summary
Researchers developed a transmitter-free system using ZnSe quantum dots and 2,5-diphenyloxazole for efficient triplet-triplet annihilation upconversion. This breakthrough achieves a record 24% upconversion quantum yield by optimizing emitter concentration.
Area of Science:
- Materials Science
- Photochemistry
- Nanotechnology
Background:
- Triplet-triplet annihilation upconversion (TTA-UC) is crucial for light harvesting but often limited by short exciton lifetimes.
- Existing methods frequently require tethered triplet transmitters, adding complexity.
- Quantum dot (QD) sensitization offers a promising pathway for TTA-UC, but efficiency remains a challenge.
Purpose of the Study:
- To develop a transmitter-free TTA-UC system using quantum dots.
- To investigate the effect of emitter concentration on upconversion efficiency.
- To achieve high upconversion quantum yield (UQY) in a QD-sensitized system.
Main Methods:
- Fabrication of a binary system comprising ZnSe quantum dots and 2,5-diphenyloxazole (DPO).
- Utilized transient spectroscopy to analyze triplet energy transfer and annihilation dynamics.
- Systematically varied DPO concentration to determine optimal conditions for UQY.
Main Results:
- Achieved a record 24% upconversion quantum yield, the highest reported for QD-sensitized TTA-UC.
- UQY peaked at 30 mM DPO concentration.
- Triplet energy transfer efficiency remained high (>80%) across concentrations, while triplet-triplet annihilation efficiency varied with DPO concentration, peaking at 25%.
Conclusions:
- Demonstrated a transmitter-free QD-sensitized TTA-UC system with unprecedented efficiency.
- Identified emitter concentration as a critical parameter for optimizing TTA-UC performance.
- Established a design principle for binary QD upconversion systems by modulating emitter concentration for maximum triplet-triplet annihilation efficiency.
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