Feng Zhaoyang, Lou Bibo, Yin Min, Yeung Yau-Yuen, Sun Hong-Tao, Duan Chang-Kui
Hefei National Laboratory for Physical Sciences at the Microscale and School of Physical Sciences, University of Science and Technology of China, Hefei 230026, China.
CAS Key Laboratory of Microscale Magnetic Resonance, University of Science and Technology of China, Hefei 230026, China.
Inorg Chem. 2021 Apr 5;60(7):4434-4446. doi: 10.1021/acs.inorgchem.0c03217. Epub 2021 Mar 18.
Bismuth ion-doped phosphate crystals have shown rich luminescence phenomena. However, the complexity and variety of Bi-related transitions bring great challenges to the understanding of the underlying mechanisms, rendering it hard to rationally design new phosphors and optimize their performance. In this work, we perform first-principles calculations based on the generalized gradient approximation of density functional to obtain the excited state equilibrium geometric structures and then calculate the electronic structures for various Bi-related excited states in phosphates RPO:Bi (R = Y, Lu, La) by utilizing the hybrid density functional method. The experimentally measured excitation and emission features are well interpreted by our theoretical calculations. Specifically, we reveal that the emission in LaPO:Bi is of charge transfer nature, whereas the dominant emission in YPO:Bi or LuPO:Bi is the characteristic A band emission. Trapped holes above the valence band maximum due to intrinsic defects are deemed to play a role in the charge-transfer emission of LaPO. Our calculations show that the excited state of the Bi pair in YPO or LuPO is (Bi-Bi)*, rather than Bi-Bi. Such a Bi pair contributes to the longer wavelength emission. Furthermore, our calculations on charge transition levels show that Bi ions can act as electron and hole traps in RPO (R = Y, Lu, La). Our work indicates that first-principles calculations can be useful in exploring the diverse luminescence processes in Bi-doped inorganic insulators.
铋离子掺杂的磷酸盐晶体呈现出丰富的发光现象。然而，与铋相关的跃迁的复杂性和多样性给理解其潜在机制带来了巨大挑战，使得合理设计新型磷光体并优化其性能变得困难。在这项工作中，我们基于密度泛函的广义梯度近似进行第一性原理计算，以获得激发态平衡几何结构，然后利用杂化密度泛函方法计算磷酸盐RPO:Bi（R = Y、Lu、La）中各种与铋相关的激发态的电子结构。我们的理论计算很好地解释了实验测量的激发和发射特征。具体而言，我们揭示了LaPO:Bi中的发射具有电荷转移性质，而YPO:Bi或LuPO:Bi中的主要发射是特征A带发射。由于本征缺陷导致的价带顶上方的捕获空穴被认为在LaPO的电荷转移发射中起作用。我们的计算表明，YPO或LuPO中铋对的激发态是(Bi-Bi)*，而不是Bi-Bi。这样的铋对有助于产生更长波长的发射。此外，我们对电荷跃迁能级的计算表明，铋离子在RPO（R = Y、Lu、La）中可以充当电子和空穴陷阱。我们的工作表明，第一性原理计算有助于探索铋掺杂无机绝缘体中的各种发光过程。
