Bright and Stable Single-Photon Emission in Zinc-Alloyed CsPbBr₃ Nanocrystals Through Controlled Auger Recombination

Single-photon sources (SPS) are indispensable for various quantum technologies. Colloidal lead halide perovskites (LHPs) have recently attracted significant attention as SPS due to their excellent electrical and optical properties at room temperature. However, their practical application is hindered by their poor stability and a trade-off between single-photon purity and non-blinking emission, the latter being essential for light-emitting diode (LED) and laser applications. In this study, Zn-alloyed CsPbBr₃ nanocrystals (Zn-NCs) are successfully synthesized using ZnBr₂ as a dopant, achieving superior optical properties compared to the undoped pristine nanocrystals (P-NCs). This approach simultaneously replaces toxic Pb²⁺ with Zn²⁺ and eliminates deep trap states associated with halide vacancies through Br^- passivation. This resulted in exceptional stability and a near-unity photoluminescence quantum yield (PLQY) of the treated nanocrystals (NCs). Single-particle photoluminescence (PL) studies reveal that Zn-NCs exhibit superior single-photon purity, reduced blinking, and greater photostability compared to their undoped counterparts. Femtosecond transient absorption spectroscopy (fs-TAS) showed that Zn alloying accelerates nonradiative Auger recombination, thereby suppressing multiphoton emission and consequently enhancing single-photon purity. By integrating results from multiple techniques, it is demonstrated that Zn²⁺ alloying in the CsPbBr₃ NC lattice significantly enhanced the stability, brightness, and single-photon purity while simultaneously minimizing the blinking.