Superflourescence (SF) represents a quantum many-body phenomena, where coherent interactions between an ensemble of emitters and radiation fields give rise to emergent spontaneously, cooperative behavior that is fundamentally different from individual emitters. The exploration of structural-functional relationships and phase transition of SF with stimulated emission (e.g., amplified spontaneous emission (ASE), lasing etc.) have garnered significant attention in both theoretical and experimental investigations. Traditional long-range ordered perovskite nanocrystal (PNC) superlattices (SL) exhibit several inherent limitations that stifled systematic investigation into SF and the interplay between SF and other stimulated emission: (i) limited ligand types that permit orderly assembly of SLs, thereby hindering detailed photophysical studies into the structure-function properties; (ii) disordered spatial distributions challenges cavity integration of SLs to allow systematic investigation of the transition between SF and lasing, (iii) dispersed SL precludes the formation of high-density films to surpass optical gain threshold of ASE.

In this work, we overcome prior limitations by harnessing long-range ordered perovskite superball (SB) superstructures as a robust and versatile platform that provides multiple tunable degrees of freedom – enabling precise control over perovskite nanocrystal (PNC) size, ligand chemistry, packing density, and cavity architecture. This platform facilitates detailed photophysical investigations across both spontaneous and stimulated emission regimes, including spontaneous emission (SE), SF, ASE, and lasing. Through systematic variation of ligand length and nanocrystal size, we identified a critical packing density (r ~0.34), above which SF is activated. The SB system also exhibits high thermal resilience, sustaining SF up to 150 K, and demonstrates over tenfold enhanced stability compared to conventional superlattices - retaining >85% of its PL intensity after 1600 hours. Notably, the interplay between SF and ASE/lasing can be modulated by tuning the emitter density or the size of the SBs.

These findings offer critical insights into the fundamental mechanisms driving both spontaneous and stimulated emissions as well as their transitions across the different realms in strongly coupled PNC systems. This understanding could pave the way for significant advancements in the development of ultrabright, coherent quantum light sources.