Roman Benjamin J, Villegas Noel Mireles, Lytle Kylie, Sheldon Matthew
Nano Lett. 2020 Dec 9;20(12):8874-8879. doi: 10.1021/acs.nanolett.0c03910. Epub 2020 Nov 16.
One photon up-conversion photoluminescence is an optical phenomenon whereby the thermal energy of a fluorescent material increases the energy of an emitted photon compared with the energy of the photon that was absorbed. When this occurs with near unity efficiency, the emitting material undergoes a net decrease in temperature, so-called optical cooling. Because the up-conversion mechanism is thermally activated, the yield of up-converted photoluminescence is also a reporter of the temperature of the emitter. Taking advantage of this optical signature, cesium lead trihalide nanocrystals are shown to cool during the up-conversion of 532 nm CW laser excitation. Raman thermometric analysis of a substrate on which the nanocrystals were deposited further verifies the decrease in the local environmental temperature by as much as 25 °C during optical pumping. This is the first demonstration of optical cooling driven by colloidal semiconductor nanocrystal up-conversion.
单光子上转换光致发光是一种光学现象，即荧光材料的热能使发射光子的能量相比于被吸收光子的能量增加。当这种现象以接近单位效率发生时，发射材料的温度会净下降，即所谓的光学冷却。由于上转换机制是热激活的，上转换光致发光的产率也是发射体温度的一个指标。利用这种光学特征，研究表明，在532 nm连续波激光激发的上转换过程中，三卤化铯铅纳米晶体会冷却。对沉积有纳米晶体的基底进行拉曼温度测量分析，进一步证实了光泵浦期间局部环境温度下降高达25℃。这是胶体半导体纳米晶体上转换驱动光学冷却的首次证明。
