Ordered assemblies of colloidal semiconductor nanocrystals have traditionally been studied for energy transfer and electronic transport arising from wavefunction overlap between neighboring nanocrystals. In this perspective, we instead focus on light‐coupled nanocrystal solids engineered primarily for light emission. These materials include ordered superlattices and compositionally doped assemblies, spanning a continuum from optically dense solids in which all nanocrystals are emissive to optically diluted solids where emitters are spatially separated by transparent filler nanocrystals. By tuning emitter density and interparticle spacing relative to the emission wavelength, light‐coupled nanocrystal solids enable access to optical regimes ranging from collective phenomena such as superfluorescence and superradiance to single‐nanocrystal and single‐photon emission. Rooted in lead halide perovskite and cadmium chalcogenide nanocrystal superlattices, this concept can be extended to heavy‐metal‐free nanocrystals and provides a materials platform for optical information processing and quantum technologies.
Dmitry Baranov (Sun,) studied this question.