Optical Properties of Single CsPbBr3 Perovskite Quantum Dots Synthesized by a Modified Ligand-Assisted Reprecipitation Method.

Colloidal perovskite quantum dots (pQDs) are promising quantum light emitters, yet single-pQD studies have so far relied mostly on hot-injection synthesis, which requires precise temperature control and an inert atmosphere. Demonstrating high optical quality at the single-emitter level is the most stringent benchmark for milder synthesis routes, which often yield structural and surface defects. Here, we show that a modified ligand-assisted reprecipitation (LARP) approach produces ∼10 nm CsPbBr3 pQDs with state-of-the-art single-emitter optical properties. Combining amine-mediated postsynthetic size-trimming with didodecyldimethylammonium bromide (DDAB) ligands for enhanced passivation and colloidal stability, we obtain isolated pQDs with stable emission and minimal spectral diffusion at cryogenic temperatures. Microphotoluminescence resolves the bright-exciton fine structure, its optical phonon replicas, and the trion and biexciton states, while time-resolved and photon-correlation measurements reveal a short emission lifetime and high-purity single-photon emission. Modified LARP thus offers an accessible, room-temperature alternative to hot injection, with added flexibility for postsynthetic ligand engineering.