Coordination-mediated cold quenching for the synthesis of strongly quantum-confined FAPbI3 quantum dots.

Strong quantum confinement can fundamentally reshape excitonic processes and radiative recombination in perovskite quantum dots (QDs), yet accessing this regime remains challenging in organic-inorganic hybrid FAPbI3 nanocrystals because of their low crystallization barrier and rapid growth. Here, we report a coordination-mediated cold quenching strategy for synthesizing strongly quantum-confined FAPbI3 QDs with tunable emission from 696 to 759 nm. The key step involves the injection of a precooled ethyl methacrylate (EMA, -70 °C), which rapidly lowers the reaction temperature while simultaneously retarding precursor conversion and suppressing QD regrowth. Such a strategy enables small QDs with an average size of 6.4 nm and a near-unity photoluminescence quantum yield. Representative light-emitting diodes based on these QDs deliver electroluminescence at 715 nm with a peak external quantum efficiency of 16.3%. This work provides a viable strategy for accessing ultrasmall hybrid perovskite QDs and advances the rational control of quantum confinement in soft ionic semiconductors.