Room-temperature exciton-polariton lasing in semiconductor colloidal quantum wells

Exciton-polariton lasing is the spontaneous coherent emission resulting from exciton-polariton Bose-Einstein condensation (BEC), facilitated by polariton-polariton simulated scattering. This process does not require population inversion, unlike conventional photonic lasers. II-VI/III-V colloidal semiconductor nanocrystals, known for their narrow emission linewidth and tunable emission wavelength, find broad applications in displays, LEDs, and detectors. However, achieving exciton-polariton lasing with these materials remains challenging. In this work, we investigate the exciton binding energy variations in CdSe colloidal quantum wells (CQWs) with different thicknesses and demonstrate the integration of CQWs in a face-down aligned configuration within a Fabry–Pérot cavity. This alignment enhances the exciton-photon coupling, leading to increased Rabi splitting energy and stronger coupling compared to randomly oriented CQWs, thereby facilitate exciton-polariton condensation. Due to the enhanced coupling with cavity fields and large exciton binding energy, we report the first observation of room-temperature exciton-polariton BEC and exciton-polariton lasing from CdSe CQWs. By systematically tuning the exciton-photon detuning, we achieve wavelength-tunable polariton lasing from 530 nm to 549 nm, including spectral regions without conventional optical gain, extending lasing beyond the intrinsic emission of 4 ML CQWs. These findings establish CdSe CQWs as effective platform for polariton-based optoelectronics.