Diroll Benjamin T, Coropceanu Igor, Portner Joshua, Hua Muchuan, Schaller Richard D, Talapin Dmitri V
Center for Nanoscale Materials, Argonne National Laboratory, 9700 S. Cass Avenue, Lemont, Illinois 60439, United States.
Department of Chemistry and James Franck Institute, University of Chicago, 5735 S. Ellis Avenue, Chicago, Illinois 60637, United States.
Nano Lett. 2025 Feb 12;25(6):2366-2372. doi: 10.1021/acs.nanolett.4c05769. Epub 2025 Feb 2.
Quantum well intersubband transitions are critical for quantum cascade lasers and infrared photodetectors. Control of band offsets allows bound-to-bound intersubband transitions, with confinement of both initial and final states, and bound-to-continuum transitions, in which only the initial state is energetically confined within the potential well. Both types of transitions are also achieved in colloidal CdSe wells by changing the heterostructure shell. Bare wells have narrow intersubband transitions spanning the near-infrared spectrum following effective mass predictions. Atomically precise core/shells enable a readily adjusted potential well for electrons. For CdSe/ZnS, bound-to-bound transitions are narrow and redshift with shell thickness. By contrast, broad bound-to-continuum absorptions are found in CdSe/CdS. Due to small conduction band offsets, higher conduction band states of the well are more delocalized into the CdS shell. These measurements provide unique data to understand the electronic structure of colloidal quantum wells and chart a path to atomically precise optoelectronic materials for the mid-infrared.
