Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
Nano Lett. 2021 Jan 27;21(2):1011-1016. doi: 10.1021/acs.nanolett.0c04060. Epub 2021 Jan 14.
Infrared-to-visible photon upconversion could benefit applications such as photovoltaics, infrared sensing, and bioimaging. Solid-state upconversion based on triplet exciton annihilation sensitized by nanocrystals is one of the most promising approaches, albeit limited by relatively weak optical absorption. Here, we integrate the upconverting layers into a Fabry-Pérot microcavity with quality factor = 75. At the resonant wavelength λ = 980 nm, absorption increases 74-fold and we observe a 227-fold increase in the intensity of upconverted emission. The threshold excitation intensity is reduced by 2 orders of magnitude to a subsolar flux of 13 mW/cm. We measure an external quantum efficiency of 0.06 ± 0.01% and a 2.2-fold increase in the generation yield of upconverted photons. Our work highlights the potential of triplet-triplet annihilation-based upconversion in low-intensity sensing applications and demonstrates the importance of photonic designs in addition to materials engineering to improve the efficiency of solid-state upconversion.
红外-可见光上转换可以使光伏、红外传感和生物成像等应用受益。基于纳米晶体敏化三重态激子湮灭的固态上转换是最有前途的方法之一，尽管其受到相对较弱的光吸收的限制。在这里，我们将上转换层集成到品质因数为 75 的法布里-珀罗微腔中。在共振波长 λ = 980nm 处，吸收增加了 74 倍，我们观察到上转换发射的强度增加了 227 倍。激发强度的阈值降低了两个数量级，达到 13mW/cm 的亚太阳光通量。我们测量得到的外量子效率为 0.06 ± 0.01%，上转换光子的产生效率提高了 2.2 倍。我们的工作强调了基于三重态-三重态湮灭的上转换在低强度传感应用中的潜力，并证明了除了材料工程之外，光子设计对于提高固态上转换效率的重要性。
