Yb3+ speciation and energy-transfer dynamics in quantum-cutting Yb3+ -doped CsPbCl3 perovskite nanocrystals and single crystals
Yb3+ speciation and energy-transfer dynamics in quantum-cutting Yb3+ -doped CsPbCl3 perovskite nanocrystals and single crystals
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DOI：
10.1103/physrevmaterials.4.105405
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发表时间：
2020-10
期刊：
影响因子：
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通讯作者：
J. Y. Roh;Matthew D. Smith;M. Crane;D. Biner;Tyler J. Milstein;K. Krämer;D. Gamelin
中科院分区：
文献类型：
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作者：
J. Y. Roh;Matthew D. Smith;M. Crane;D. Biner;Tyler J. Milstein;K. Krämer;D. Gamelin
掺Yb3+的无机金属卤化物钙钛矿(Yb3+：CsPbX3，X=Cl，Br3+)是一种高效的量子切割材料，其吸收的蓝光或紫外光的能量被Yb3+以近红外光子对的形式重新发射出去。实验光致发光量子产率已达到200{%}。作为第一种结合了如此高的光致发光量子产率和对可见光的强宽带吸收的量子切割材料，这些材料为提高太阳能技术的效率提供了独特的机会。然而，人们对这种量子切割的根本起源知之甚少。在这里，我们描述了Yb3+：CsPbCl3两种不同形式的变温和时间分辨光致发光研究-胶体纳米晶体和宏观单晶。这两种形式表现出非常相似的光谱性质，表明量子切割是Yb3+：CsPbX3成分本身的一种本征性质。低温光致发光光谱观察到两种形式的Yb3+以不同的形式存在，但值得注意的是，在这两种情况下，量子切割都是由相同的特定Yb3+物种主导的。时间分辨光致发光测量为量子切割机制中先前假设的中间状态提供了直接证据。这一中间态起到了从钙钛矿的光生激发态到Yb3+发射激发态的驰豫作用，因此具有重要的力学意义。在室温下，这种中间态在几皮秒内被填充，并且在纳米晶体和单晶Yb3+：CsPbCl3中只有~7 ns的衰减时间。文中还讨论了这些观测结果的力学含义。
Yb3+-doped inorganic metal-halide perovskites (Yb3+:CsPbX3, X = Cl, Br) have recently been discovered to display highly efficient quantum cutting, in which the energy from individual blue or UV photons absorbed by the material is re-emitted in the form of pairs of near-infrared photons by Yb3+ dopants. Experimental photoluminescence quantum yields approaching 200{%} have been reported. As the first quantum-cutting materials that combine such high photoluminescence quantum yields with strong, broadband absorption in the visible, these materials offer unique opportunities for enhancing the efficiencies of solar technologies. Little is known about the fundamental origins of this quantum cutting, however. Here, we describe variable-temperature and time-resolved photoluminescence studies of Yb3+:CsPbCl3 in two disparate forms - colloidal nanocrystals and macroscopic single crystals. Both forms show very similar spectroscopic properties, demonstrating that quantum cutting is an intrinsic property of the Yb3+:CsPbX3 composition itself. Diverse Yb3+ speciation is observed in both forms by low-temperature photoluminescence spectroscopy, but remarkably, quantum cutting is dominated by the same specific Yb3+ species in both cases. Time-resolved photoluminescence measurements provide direct evidence of the previously hypothesized intermediate state in the quantum-cutting mechanism. This intermediate state mediates relaxation from the photogenerated excited state of the perovskite to the emissive excited state of Yb3+, and hence is of critical mechanistic importance. At room temperature, this intermediate state is populated within a few picoseconds and has a decay time of only ~ 7 ns in both nanocrystalline and single-crystal Yb3+:CsPbCl3. The mechanistic implications of these observations are discussed.