Weakly Confined Organic-Inorganic Halide Perovskite Quantum Dots as High-Purity Room-Temperature Single Photon Sources.

Colloidal perovskite quantum dots (PQDs) have emerged as highly promising single photon emitters for quantum information applications. Presently, most strategies have focused on leveraging quantum confinement to increase the nonradiative Auger recombination (AR) rate to enhance single-photon (SP) purity in all-inorganic CsPbBr 3 QDs. However, this also increases the fluorescence intermittency. Achieving high SP purity and blinking mitigation simultaneously remains a significant challenge. Here, we transcend this limitation with room-temperature synthesized weakly confined hybrid organic-inorganic perovskite (HOIP) QDs. Superior single photon purity with a low g (2) (0) < 0.07 ± 0.03 and a nearly blinking-free behavior (ON-state fraction >95%) in 11 nm FAPbBr 3 QDs are achieved at room temperature, attributed to their long exciton lifetimes ( τ X ) and short biexciton lifetimes ( τ XX ). The significance of the organic A-cation is further validated using the mixed-cation FA x Cs 1- x PbBr 3 . Theoretical calculations utilizing a combination of the Bethe-Salpeter (BSE) and k·p approaches point toward the modulation of the dielectric constants by the organic cations. Importantly, our findings provide valuable insights into an additional lever for engineering facile-synthesized room-temperature PQD single photon sources.