Lanthanide-based photon-cutting phosphors absorb high-energy photons and ‘cut’ them into multiple smaller excitation quanta. These quanta are subsequently emitted, resulting in photon-conversion efficiencies exceeding unity. The photon-cutting process relies on energy transfer between optically active lanthanide ions doped in the phosphor. However, it is not always easy to determine, let alone predict, which energy-transfer mechanisms are operative in a particular phosphor. This makes the identification and design of new promising photon-cutting phosphors difficult. Here we unravel the possibility of using the Tm³⁺/Yb³⁺ lanthanide couple for photon cutting. We compare the performance of this couple in four different host materials. Cooperative energy transfer from Tm³⁺ to Yb³⁺ would enable blue-to-near-infrared conversion with 200% efficiency. However, we identify phonon-assisted cross-relaxation as the dominant Tm³⁺-to-Yb³⁺ energy-transfer mechanism in YBO₃, YAG, and Y₂O₃. In NaYF₄, in contrast, the low maximum phonon energy renders phonon-assisted cross-relaxation impossible, making the desired cooperative mechanism the dominant energy-transfer pathway. Our work demonstrates that previous claims of high photon-cutting efficiencies obtained with the Tm³⁺/Yb³⁺ couple must be interpreted with care. Nevertheless, the Tm³⁺/Yb³⁺ couple is potentially promising, but the host material—more specifically, its maximum phonon energy—has a critical effect on the energy-transfer mechanisms and thereby on the photon-cutting performance.

基于镧系元素的光子切割磷光体吸收高能光子，并将它们“切割”成多个较小的激发量子。这些量子随后被发射，导致光子转换效率超过一。光子切割过程依赖于荧光粉中掺杂的光学活性镧系元素离子之间的能量转移。但是，要确定（更不用说预测）在特定的荧光粉中哪些能量传递机制起作用并不总是那么容易。这使得难以鉴定和设计新的有前途的光子切割磷光体。在这里，我们探讨了使用Tm ³⁺ / Yb ³⁺镧系对进行光子切割的可能性。我们在四种不同的主机材料中比较了这对夫妇的性能。来自Tm ^3+的协同能量转移如果将其转换为Yb ^3+，则可以实现200％效率的蓝到近红外转换。但是，我们将声子辅助的交叉松弛确定为YBO ₃，YAG和Y ₂ O _3中主要的Tm ³⁺到Yb ³⁺能量转移机制。相反，在NaYF ₄中，低的最大声子能量使声子辅助的交叉弛豫成为不可能，从而使所需的协同机制成为主要的能量传递途径。我们的工作表明，以前对通过Tm ³⁺ / Yb ³⁺对获得的高光子切割效率的主张必须谨慎解释。尽管如此，Tm ³⁺ / Yb ³⁺ 偶极有潜力，但是主体材料（更具体地讲，其最大声子能量）对能量传递机制并因此对光子切割性能具有关键影响。