Sequential-temperature atomic layer deposition strategy resolves passivation-densification dilemma in CsPbBr3 perovskite quantum dots

Atomic layer deposition (ALD) presents a promising avenue for improving the environmental stability of perovskite quantum dots (PQDs). However, standard ALD processes (120–200 °C) inevitably compromise the PQD lattice structure, while lower temperatures yield porous, non-protective films. To overcome this trade-off, we developed a sequential-temperature ALD strategy that synergizes low-temperature surface passivation with high-temperature densification. First, a low-temperature (65 °C) ALD stage deposits a surface modification layer around PQDs, which leverages energetic precursor molecules to selectively passivate surface/lattice defects, effectively suppressing non-radiative recombination within PQDs and boosting their luminescence efficiency. Crucially, this initial layer plays a pivotal role in preventing thermal degradation of the perovskite during subsequent processing and generates a hydroxyl‑rich surface. These reactive sites facilitate the second stage, a high-temperature (120 °C) ALD, to rapidly deposit a dense Al 2 O 3 protective barrier layer. Remarkably, this sequential process induces the formation of a chemically graded Pb–O–Al–O–Al 2 O 3 interfacial structure remediating defects within the initial layer, exhibiting intrinsic self-healing capability. The resulting CsPbBr 3 /Al 2 O 3 composite manifests exceptional environmental stability, particularly against moisture, representing one of the best performances reported to date for ALD-encapsulated bulk CsPbBr 3 films. Unlike complex hybrid encapsulation schemes, our streamlined, standalone ALD approach enables scalable PQD modification. White light-emitting diodes fabricated with these encapsulated PQDs demonstrate a wide color gamut (∼120% NTSC) and remarkable spectral stability. This work establishes a generalizable paradigm for ALD encapsulation of thermally sensitive materials.