Debye Institute for Nanomaterials Science, Utrecht University, Princetonplein 1, 3584 CC Utrecht, The Netherlands.
Nat Commun. 2017 May 24;8:15537. doi: 10.1038/ncomms15537.
In optical materials energy is usually extracted only from the lowest excited state, resulting in fundamental energy-efficiency limits such as the Shockley-Queisser limit for single-junction solar cells. Photon-cutting materials provide a way around such limits by absorbing high-energy photons and 'cutting' them into multiple low-energy excitations that can subsequently be extracted. The occurrence of photon cutting or quantum cutting has been demonstrated in a variety of materials, including semiconductor quantum dots, lanthanides and organic dyes. Here we show that photon cutting results in bunched photon emission on the timescale of the excited-state lifetime, even when observing a macroscopic number of optical centres. Our theoretical derivation matches well with experimental data on NaLaF:Pr, a material that can cut deep-ultraviolet photons into two visible photons. This signature of photon cutting can be used to identify and characterize new photon-cutting materials unambiguously.
在光学材料中，能量通常仅从最低激发态中提取，这导致了基本的能量效率限制，例如单结太阳能电池的肖克利-奎塞尔限制。光子切割材料通过吸收高能光子并将其“切割”成多个低能量激发态，从而提供了一种规避此类限制的方法，这些激发态随后可以被提取出来。光子切割或量子切割已经在多种材料中得到了证实，包括半导体量子点、镧系元素和有机染料。在这里，我们表明，即使在观察大量光学中心时，光子切割也会导致在激发态寿命的时间尺度上发生聚集的光子发射。我们的理论推导与 NaLaF:Pr 的实验数据非常吻合，NaLaF:Pr 是一种可以将深紫外光子切割成两个可见光光子的材料。这种光子切割的特征可用于明确识别和表征新的光子切割材料。
