Perovskite nanocrystals as emerging single-photon emitters: Progress, challenges, and opportunities

Metal-halide perovskite nanocrystals (PNCs) have emerged as leading candidates for next-generation quantum emitters (QEs), offering a unique combination of high photoluminescence quantum yield, tunable emission, short radiative lifetimes, and record-high single-photon purity under ambient conditions. These properties, together with low-cost and scalable solution-phase fabrication, position PNCs as attractive alternatives to traditional epitaxial and colloidal quantum dots. In this review, we outline the physical parameters that define quantum emission in PNCs, compare their performance to other established and emerging QEs, and assess the key figures of merit, including photostability, single-photon purity, and photon indistinguishability, required for practical quantum applications. We discuss underlying mechanisms affecting PNC emission behavior and highlight recent advances in improving their quantum emitting properties through synthetic and photonic engineering approaches. While challenges related to environmental stability and photon indistinguishability remain, emerging strategies, such as surface passivation, metal-ion doping, and coupling with electromagnetic nano- and microcavities, are steadily closing the gap between PNCs and ideal quantum light sources.