中文 |

New Energy Transfer Mechanism Enhances Red Emission in Upconversion Systems

Author: HOU Xinjiang |

Researchers at the Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, have uncovered an innovative energy transfer mechanism that significantly enhances the red emission in upconversion systems. Published in The Journal of Physical Chemistry Letters, the study focuses on the Er3+/Yb3+ system, commonly used in luminescent materials, and reveals a new round-trip energy transfer (RTET) process that provides superior red emission performance.
Upconversion systems are key to technologies like display devices, solar cells, and bioimaging, where materials absorb low-energy near-infrared (NIR) light and re-emit it as visible light. In the case of Er3+/Yb3+ co-doped systems, the typical upconversion luminescence (UCL) produces green and red emissions, with the red emission being of particular interest for its potential in various applications. However, achieving efficient red emission has been challenging due to the limitations of traditional energy transfer mechanisms.
The researchers discovered that the RTET process, involving energy transfer between Er3+ and Yb3+  ions, dominates the red emission mechanism. This process, previously unexplored in detail, operates through two distinct steps. First, energy is transferred from Er3+ to Yb3+, followed by a reverse energy transfer that excites Er3+ from a lower state to a red-emitting state. This RTET mechanism not only enhances the intensity of red emission but also significantly alters the temporal dynamics of the emitted light.
The study demonstrated that RTET enhances the red-to-green emission ratio (R/G) across various Yb3+ concentrations. With the increase in Yb3+ content, the RTET mechanism becomes more dominant, reaching efficiencies exceeding 90% for Yb3+ concentrations of 10% or more. This breakthrough also resulted in faster red emission, with the decay time of the red light becoming similar to that of the green light, showcasing the efficiency of the RTET process.
The results provide a deep understanding of how RTET influences the color and temporal behavior of upconversion luminescence in the Er3+/Yb3+system. Notably, RTET has the potential to improve applications in fields that require precise control over light emission, such as in optical thermometry, bioimaging, and anti-counterfeiting technologies.
The efficiency of RTET is particularly beneficial for devices that rely on high-quality red emission, such as lasers, light-emitting diodes (LEDs), and photovoltaic systems. The study's findings pave the way for improving these technologies by using co-doped materials that enhance upconversion efficiency.
Additionally, the study provides crucial insights into how the concentration of Yb3+ ions can be tuned to optimize the red emission. This ability to fine-tune emission properties is key for developing more efficient materials for smart windows, displays, and even medical imaging devices.
With the potential to regulate the color and intensity of luminescence more effectively than traditional methods, RTET represents a promising direction for future research. The authors suggest that further exploration into the interaction dynamics between Er3+ and Yb3+ ions could lead to even greater enhancements in luminescence properties, paving the way for innovative applications in multiple industries.


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WU Hao

Changchun lnstitute of Optics, Fine Mechanics and Physics

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