Dai Yuchen, Qi Pengfei, Tao Guangyi, Yao Guangjie, Shi Beibei, Liu Zhixin, Liu Zhengchang, He Xiao, Peng Pu, Dang Zhibo, Zheng Liheng, Zhang Tianhao, Gong Yongji, Guan Yan, Liu Kaihui, Fang Zheyu
School of Physics, State Key Laboratory for Mesoscopic Physics, Academy for Advanced Interdisciplinary Studies, Collaborative Innovation Center of Quantum Matter, Nano-optoelectronics Frontier Center of Ministry of Education, Peking University, 100871, Beijing, China.
Institute of Modern Optics, Nankai University, Tianjin Key Laboratory of Micro-scale Optical Information Science and Technology, 300350, Tianjin, China.
Light Sci Appl. 2023 Jan 2;12(1):6. doi: 10.1038/s41377-022-01051-9.
Phonon-assisted photon upconversion (UPC) is an anti-Stokes process in which incident photons achieve higher energy emission by absorbing phonons. This letter studies phonon-assisted UPC in twisted 2D semiconductors, in which an inverted contrast between UPC and conventional photoluminescence (PL) of WSe twisted bilayer is emergent. A 4-fold UPC enhancement is achieved in 5.5° twisted bilayer while PL weakens by half. Reduced interlayer exciton conversion efficiency driven by lattice relaxation, along with enhanced pump efficiency resulting from spectral redshift, lead to the rotation-angle-dependent UPC enhancement. The counterintuitive phenomenon provides a novel insight into a unique way that twisted angle affects UPC and light-matter interactions in 2D semiconductors. Furthermore, the UPC enhancement platform with various superimposable means offers an effective method for lighting bilayers and expanding the application prospect of 2D stacked van der Waals devices.
声子辅助光子上转换（UPC）是一种反斯托克斯过程，其中入射光子通过吸收声子实现更高能量的发射。本文研究了扭曲二维半导体中的声子辅助UPC，其中WSe扭曲双层的UPC与传统光致发光（PL）之间出现了反转对比度。在5.5°扭曲双层中实现了4倍的UPC增强，而PL减弱了一半。晶格弛豫驱动的层间激子转换效率降低，以及光谱红移导致的泵浦效率提高，导致了与旋转角度相关的UPC增强。这种违反直觉的现象为扭曲角度影响二维半导体中的UPC和光与物质相互作用的独特方式提供了新的见解。此外，具有各种可叠加方式的UPC增强平台为照亮双层和扩展二维堆叠范德华器件的应用前景提供了一种有效方法。
