Yu Dechao, Ballato John, Riman Richard E
Department of Materials Science and Engineering, Rutgers, The State University of New Jersey, 607 Taylor Road, Piscataway, NJ 08854, United States.
The Center for Optical Materials Science and Engineering, Technologies (COMSET), Department of Material Science and Engineering, Clemson University, SC 29634, United States.
J Phys Chem C Nanomater Interfaces. 2016 May 12;120(18):9958-9964. doi: 10.1021/acs.jpcc.6b01466. Epub 2016 Apr 5.
Rare-earth ions are used in a wide range of emissive devices - ranging from lasers to displays - where high optical efficiency and narrow-linewidth are important. While their radiative properties are important, nonradiative properties are also critical since they can reduce optical efficiency and generate heat. In this paper, theories for multiphonon relaxation rate are reviewed for rare-earth excited states in solid-state dielectric hosts. A range of various approaches are used to simplify the mathematical form of the rate equations. The H excited state of Er, responsible for a technologically significant green emission, is modeled to show how the various theories manifest an order-of-magnitude variation in the thermal dependence of the multiphonon relaxation rate, as well as anomalous local minima in phonon scattering for temperatures above 0 K. This work proposes a corrective term of two quanta (Δν= + 2) of the mediating phonon energy to energy gap, so the calculated and the experimentally determined relaxation rates are equal. Radiative quantum efficiencies of both the G→H ~1.3 m and F→F ~7 m of Pr are calculated to show the importance of both proper measurement of phonon energy and application of the multiphonon relaxation rate theory.
稀土离子被广泛应用于从激光到显示器等各种发光器件中，在这些器件中，高光效率和窄线宽非常重要。虽然它们的辐射特性很重要，但非辐射特性也至关重要，因为它们会降低光效率并产生热量。本文综述了固态介电基质中稀土激发态的多声子弛豫速率理论。采用了一系列不同的方法来简化速率方程的数学形式。对铒的H激发态进行建模，该激发态产生具有重要技术意义的绿色发射，以展示各种理论如何在多声子弛豫速率的热依赖性上表现出数量级的变化，以及在高于0 K的温度下声子散射中的异常局部最小值。这项工作提出了一个中介声子能量的两个量子（Δν = + 2）到能隙的校正项，从而使计算得到的弛豫速率与实验测定的弛豫速率相等。计算了镨的G→H ~1.3 m和F→F ~7 m的辐射量子效率，以表明正确测量声子能量和应用多声子弛豫速率理论的重要性。
