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
We developed a transmitter-free system using ZnSe quantum dots and 2,5-diphenyloxazole for efficient triplet-triplet annihilation upconversion. This system achieved 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 in quantum dot (QD) sensitizers.
- Existing methods typically require tethered triplet transmitters, adding complexity and potentially hindering efficiency.
Purpose of the Study:
- To develop a transmitter-free TTA-UC system using ZnSe quantum dots (QDs) and 2,5-diphenyloxazole (OXZD).
- To achieve high upconversion quantum yield (UCQY) by optimizing the concentration of the emitter molecule.
- To elucidate the relationship between emitter concentration, triplet energy transfer, and triplet-triplet annihilation efficiencies.
Main Methods:
- Fabrication of a binary system comprising ZnSe QDs and OXZD.
- Measurement of UCQY at varying OXZD concentrations using a transmitter-free approach.
- Utilizing transient spectroscopy to analyze triplet energy transfer and triplet-triplet annihilation dynamics.
Main Results:
- Achieved a record 24% UCQY, the highest reported for QD-sensitized TTA-UC.
- UCQY peaked at 30 mM OXZD concentration.
- Triplet energy transfer efficiency remained high (>80%) across concentrations, while triplet-triplet annihilation efficiency varied significantly with OXZD concentration, peaking at 25%.
Conclusions:
- Demonstrated a novel transmitter-free QD-sensitized TTA-UC system with unprecedented efficiency.
- Identified emitter concentration as a critical parameter for optimizing TTA-UC, directly impacting triplet-triplet annihilation efficiency.
- Established a design principle for binary QD upconversion systems by modulating emitter concentration for maximum performance.
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