Enhanced Performance of Two-Photon Excited Amplified Spontaneous Emission by Cd-Alloyed CsPbBr₃ Nanocrystals

It has been demonstrated that the alloyed perovskite nanocrystals (NCs) with a small amount of Cd element may passivate the inherent halide vacancies in perovskite NCs and improve their stability. However, the study of the optical properties of such alloyed perovskite NCs still remains essentially untouched, which will seriously hinder relevant applications. Herein, using different amounts of CdBr₂ as an alloyed metal precursor, a series of CsPbCd_1-Br₃ NCs (x = 1, 0.93, and 0.88) were synthesized. Compared with bare CsPbBr₃ NCs, the Cd-alloyed NCs exhibited a near-unity photoluminescence quantum yield (99%), efficiently improved stability, and enhanced electron-phonon coupling strength. As the Cd-alloyed amount was increased, their hot-carrier cooling time became faster and the exciton-biexciton interaction decreased, causing a decreased threshold of two-photon excited amplified spontaneous emission (ASE) from 1.58 to 1.23 mJ cm^-2. In addition, the Cd-alloying method can also improve the photostability of ASE, resulting in the initial ASE intensity remaining at 90% even after 7.5 × 10⁵ pulse shots. This work implies that the Cd-alloyed CsPbBr₃ NCs will be promising for application in a laser gain medium.