Upconverted electroluminescence via Auger scattering of interlayer excitons in van der Waals heterostructures

• Published in: Nature communications Vol. 10; no. 1; p. 2335
• Main Authors: Binder, J., Howarth, J., Withers, F., Molas, M. R., Taniguchi, T., Watanabe, K., Faugeras, C., Wysmolek, A., Danovich, M., Fal’ko, V. I., Geim, A. K., Novoselov, K. S., Potemski, M., Kozikov, A.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 27.05.2019; Nature Publishing Group; Nature Portfolio
• Subjects: 639/301/1005; 639/925; Augers; Carrier density; Condensed Matter; Electric fields; Electrodes; Electroluminescence; Emission spectra; Emissions; Energy transfer; Excitons; Graphene; Heterostructures; Holes (electron deficiencies); Humanities and Social Sciences; Interlayers; Light emission; Molybdenum disulfide; multidisciplinary; Optical pumping; Physics; Pumping rates; Radiative recombination; Recombination; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-019-10323-9

The intriguing physics of carrier-carrier interactions, which likewise affect the operation of light emitting devices, stimulate the research on semiconductor structures at high densities of excited carriers, a limit reachable at large pumping rates or in systems with long-lived electron-hole pairs. By electrically injecting carriers into WSe 2 /MoS 2 type-II heterostructures which are indirect in real and k-space, we establish a large population of typical optically silent interlayer excitons. Here, we reveal their emission spectra and show that the emission energy is tunable by an applied electric field. When the population is further increased by suppressing the radiative recombination rate with the introduction of an hBN spacer between WSe 2 and MoS 2 , Auger-type and exciton-exciton annihilation processes become important. These processes are traced by the observation of an up-converted emission demonstrating that excitons gaining energy in non-radiative Auger processes can be recovered and recombine radiatively. The authors present electroluminescence measurements of light-emitting devices based on van der Waals heterostructures, and observe a lower than expected threshold voltage for intralayer electroluminescence, attributed to non-radiative Auger-type recombination of interlayer excitons and resulting energy transfer.