Increasing demand for near-infrared-II (NIR-II) light sources requires improved NIR-II phosphors. We present a series of phosphors codoped with Cr³⁺ and Ni²⁺ that possess NIR-II emission with an unprecedented internal quantum efficiency (IQE) of 97.4%. Our study reveals an energy transfer mechanism involving clusters of Cr³⁺ where luminescent centers are closely matched in energy and where the Ni²⁺ emission intensity can be tuned through sintering temperature. The profound electron paramagnetic resonance (EPR) studies disclose the interaction between Cr³⁺ clusters and Cr³⁺–Ni²⁺ pairs, further proving the cause of such a high IQE and the significance of Cr³⁺ clusters. This work provides promising pathways for the development of NIR-II light-emitting diodes with outstanding efficiency by suggesting a new energy transfer source of Cr³⁺.

中文翻译：

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Cr3+团簇到Ni2+能量转移实现超高量子效率近红外-II发射

对近红外 II (NIR-II) 光源日益增长的需求需要改进的 NIR-II 荧光粉。我们推出了一系列 Cr ³⁺和 Ni ²⁺共掺杂的荧光粉，它们具有 NIR-II 发射，内量子效率 (IQE) 达到前所未有的 97.4%。我们的研究揭示了涉及 Cr ³⁺簇的能量转移机制，其中发光中心的能量紧密匹配，并且 Ni ^{2+ 的}发射强度可以通过烧结温度来调节。深入的电子顺磁共振（EPR）研究揭示了Cr ³⁺团簇与Cr ³⁺ -Ni ²⁺对之间的相互作用，进一步证明了如此高IQE的原因以及Cr ³⁺团簇的重要性。这项工作通过提出一种新的Cr ³⁺能量转移源，为开发具有出色效率的NIR-II 发光二极管提供了有前景的途径。