A hierarchical shell locks and stabilizes perovskite nanocrystals with near-unity quantum yield.

Solid-state emitters have exhibited external quantum yields (EQYs) below 65%, with no system combining unity photoluminescence quantum yield (PLQY) and commercially viable stability. These limitations are most pronounced in colloidal perovskite nanocrystals (PeNCs), given their soft ionic lattices and labile surfaces. We introduce a hierarchical shell (HS) structure comprising interbonded PbSO4-SiO2-polymer multilayers that simultaneously locks and stabilizes soft lattices and labile interfaces. HS-CsPbBr3 PeNC films exhibit T90 (10% PLQY loss) = 3211 hours under accelerated 60°C, 90% relative humidity (RH) and T90 = 12,000 hours under blue-light exposure. HS strategy generalizes across PeNC compositions-including mixed-halide, mixed-cation, iodide, and hybrid PeNCs-and enables MAPbBr3 with extended T90 = 3900 hours (60°C, 90% RH) and T90 = 27,234 hours (blue light). Moreover, HS-MAPbBr3 films with 100.0% PLQY eliminate self-absorption losses and achieve an EQY of 91.4%, approaching the theoretical maximum. The HS barrier also prevents lead leakage for safety of large-area, high-resolution displays and bio-optoelectronics.