Proxies from Ab Initio Calculations for Screening Efficient Ce3+ Phosphor Hosts
Proxies from Ab Initio Calculations for Screening Efficient Ce3+ Phosphor Hosts
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DOI：
10.1021/jp405858e
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发表时间：
2013-09-05
影响因子：
3.7
通讯作者：
Seshadri, Ram
中科院分区：
文献类型：
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作者：
Brgoch, Jakoah;DenBaars, Steven P.;Seshadri, Ram
高效的磷光体性能，意味着高光致发光量子产率（Phi），需要Ce 3+离子被托管在刚性晶体结构中。当磷光体在稍微升高的温度下操作时，这是特别重要的，这在高亮度磷光体转换的白色固态发光二极管中变得常规。我们发现，德拜温度（θ（D））的未掺杂的主机晶体结构，这是很容易计算的准谐波近似内的从头计算方法，是一个有用的代理结构刚度。这里发现θ（D）与许多Ce 3+磷光体的实验测量的θ（10）很好地相关。除了是刚性的之外，主体晶格必须具有足够大的带隙（E-g），使得Ce 3 + 4f到Sd的跃迁可以在没有来自主体能量通道的干扰的情况下发生。作为具有高Phi的有效主机的排序图，我们建议使用主机的E-g，也容易使用混合泛函以高可靠性计算，作为轴之一，Theta（D）作为另一个。这样的图被用于对我们迄今为止测试的磷光体主体进行分组。有趣的是，注意到大的E-g和高Theta（D）通常是禁忌的，这表明在寻找新的主体结构中存在挑战。虽然该策略在此应用于具有Ce 3+作为活化剂离子的氧化物主体，但其可转移到其他类别的主体化合物，并且也可转移到基于Eu 2+的磷光体。
Efficient phosphor performance, meaning a high photoluminescence quantum yield (Phi), requires the Ce3+ ion to be hosted in a rigid crystal structure. This is particularly important when the phosphor is operated at slightly elevated temperatures, as is becoming conventional in high brightness, phosphor-converted white solid-state lightemitting diodes. We find the Debye temperature (Theta(D)) of the undoped host crystal structure, which is readily calculated using ab initio methods within the quasi-harmonic approximation, is a useful proxy for structural rigidity. Theta(D) is found here to correlate well with the experimentally measured (10 for a number of Ce3+ phosphors. In addition to being rigid, the host lattice must possess a large enough band gap (E-g) that the Ce3+ 4f to Sd transition can occur without interference from a host energy channel. As a sorting diagram for efficient hosts with high Phi, we propose using E-g of the host, also readily calculated with high reliability using hybrid functionals, as one of the axes and Theta(D) as the other. Such a diagram is used to group the phosphor hosts that we have tested so far. It is interesting to note that a large E-g and high Theta(D) are often contraindicated, suggesting a challenge in the search for new host structures. While the strategy is applied here for oxides hosts with Ce3+ as the activator ion, it is transferable to other classes of host compounds, and to Eu2+ based phosphors as well.