Paradox in Visible‐Light: O 2 •‒ Generation by CsPbBr 3 Perovskite Nanocrystals

ABSTRACT CsPbBr 3 nanocrystals are often dismissed as unstable under ambient conditions, with molecular oxygen seen as their chief adversary. In this Perspective, we overturn this perception by reframing oxygen as both a catalyst of degradation and a catalyst of innovation. Under visible‐light excitation, oxygen readily converts into reactive species such as superoxide radical anions, which destabilize the lattice but simultaneously unlock unique aerobic photocatalytic pathways. We highlight how this paradox, instability as reactivity, positions CsPbBr 3 not merely as fragile optoelectronic materials but as adaptive nanocatalysts for selective bond constructions and oxidative transformations. By integrating insights from defect chemistry, surface passivation, and synthetic methodology, we argue that the so‐called weakness of these nanocrystals can be transforms into their greatest strength: a platform where environmental sensitivity is leveraged as a chemical opportunity.