Hybrid CsPbBr3 superlattice/Ag microcavity enabling strong exciton–photon coupling for low-threshold continuous-wave pumped polariton lasing†

Abstract

Achieving strong exciton–photon coupling in perovskite microcavities opens new possibilities for continuous-wave (CW) perovskite lasers with ultralow thresholds. A CsPbBr₃ superlattice (SL), assembled from quantum dots (QDs) with a narrow size distribution, offers both large oscillator strengths and extended exciton dephasing times, rendering it a highly promising platform for enhanced light–matter interactions. Nevertheless, realizing robust exciton–photon coupling in a CsPbBr₃ SL-based microcavity for low-threshold lasing remains elusive. Here, we demonstrate a hybrid microcavity integrating a CsPbBr₃ SL with a thin Ag film to boost exciton–photon coupling and achieve CW-pumped polariton lasing. Using an acetone-assisted self-assembly approach, we obtain high-quality CsPbBr₃ SLs characterized by narrow emission linewidths, large exciton binding energies, diminished exciton–phonon coupling, and highly stable amplified spontaneous emission. Optical scattering and photoluminescence measurements indicate significant coupling between the SL excitons and resonant photon modes in the CsPbBr₃/Ag microcavity. We attribute this enhanced light–matter interaction to comparable linewidths of the exciton resonance and photon mode, facilitated by the Ag film. A coupled oscillator model fit yields a Rabi splitting of approximately 225 meV in a large microcavity. Notably, we achieve CW-pumped polariton lasing near the lower polariton branch bottleneck at a low threshold of about 220 W cm⁻². Our findings elucidate the fundamental mechanism underlying strong exciton–photon coupling in CsPbX₃ SL systems and offer a viable strategy for designing CW-pumped polariton lasers with improved performance.