Enhanced interlayer neutral excitons and trions in trilayer van der Waals heterostructures

• Published in: NPJ 2D materials and applications 2018-09, Vol.2 (1), Article 30
• Main Authors: Choi, Chanyeol, Huang, Jiahui, Cheng, Hung-Chieh, Kim, Hyunseok, Vinod, Abhinav Kumar, Bae, Sang-Hoon, Özçelik, V. Ongun, Grassi, Roberto, Chae, Jongjae, Huang, Shu-Wei, Duan, Xiangfeng, Kaasbjerg, Kristen, Low, Tony, Wong, Chee Wei
• Format: Article
• Language: English
• Subjects: 639/301/357; 639/624; 639/766/1130; 639/925; Absorbance; Alignment; Chemistry and Materials Science; Cryogenic temperature; Density functional theory; Emission analysis; Excitons; First principles; Heterostructures; Holes (electron deficiencies); Interlayers; Light emission; Materials Science; Molybdenum compounds; Nanotechnology; Optimization; Optoelectronics; Photoluminescence; Radiative recombination; Surfaces and Interfaces; Temperature dependence; Thin Films; Time dependence; Trions
• ISSN: 2397-7132; 2397-7132
• DOI: 10.1038/s41699-018-0075-1

Vertically stacked van der Waals heterostructures constitute a promising platform for providing tailored band alignment with enhanced excitonic systems. Here, we report observations of neutral and charged interlayer excitons in trilayer WSe 2 –MoSe 2 –WSe 2 van der Waals heterostructures and their dynamics. The addition of a WSe 2 layer in the trilayer leads to significantly higher photoluminescence quantum yields and tunable spectral resonance compared to its bilayer heterostructures at cryogenic temperatures. The observed enhancement in the photoluminescence quantum yield is due to significantly larger electron–hole overlap and higher light absorbance in the trilayer heterostructure, supported via first-principles pseudopotential calculations based on spin-polarized density functional theory. We further uncover the temperature- and power-dependence, as well as time-resolved photoluminescence of the trilayer heterostructure interlayer neutral excitons and trions. Our study elucidates the prospects of manipulating light emission from interlayer excitons and designing atomic heterostructures from first-principles for optoelectronics. Optical physics: neutral and charged interlayer excitons in WSe 2 -MoSe 2 -WSe 2 heterostructures Trilayer heterostructures have enhanced Coulomb interactions due to interlayer radiative recombination of neutral and charged excitons. A team led by Chee Wei Wong at the University of California, Los Angeles, fabricated type-II vertical van der Waals heterostructures consisting of a trilayer WSe 2 -MoSe 2 -WSe 2 stack. Optimisation of the electronic band alignment by means of spin-polarized density functional theory allowed efficient interlayer radiative recombination. As a result, an order-of-magnitude increase of the photoluminescence quantum yield was obtained compared to bilayer heterostructures, and this was attributed to the larger electron-hole overlap and higher light absorbance in the trilayer stack, along with the formation of the neutral interlayer exciton. These results shed light to the underlying physics of light emission from interlayer excitons, and may pave the way to optimal design of van der Waals heterostructures with enhanced excitonic properties.