From atomic interfaces to scalable nanocrystal light-emitting diodes

Atomic layer deposition (ALD) heralds a paradigm-shifting revolution in atomic-scale interface engineering for semiconductor nanocrystal light-emitting diodes (SNC-LEDs), elegantly unifying colloidal quantum dots (cQDs) and metal-halide perovskite emitters through its hallmark sequential, self-limiting surface reactions—fundamentally distinguishing ALD from chemical vapor deposition (CVD), physical vapor deposition (PVD, e.g., sputtering), and solution processing (e.g., spin-coating and inkjet printing) to deliver sub-angstrom thickness mastery, defect-minimal conformality, and chemically abrupt interfaces that enable exquisite, orthogonal orchestration of energy-level alignment, charge injection/extraction dynamics, exciton confinement, and environmental resilience across intricate multilayer architectures. Ultrathin oxides (e.g., aluminum trioxide (Al2O3), zinc oxide (ZnO), titanium oxide (TiO2), magnesium oxide (MgO), and nickel oxide (NiO)) grown by ALD emerge as multifunctional interfacial constructs of unparalleled sophistication, simultaneously passivating trap states, stabilizing ligand shells, engineering charge-selective contacts, optimizing optical microcavities, and erecting diffusion barriers—seamlessly translating nanoscale chemical precision into transformative macroscopic leaps in radiative efficiency, spectral purity, and operational longevity. This review unveils trailblazing ALD and ALD-inspired frontiers—plasma-enhanced atomic layer deposition (PEALD) nitrides (e.g., aluminum nitride (AlN), hafnium nitride (HfN), and titanium nitride (TiN)), colloidal ALD (c-ALD)-like chalcogenide shells (e.g., zinc sulfide (ZnS) and cadmium sulfide (CdS)), and molecular layer deposition (MLD) organic–inorganic hybrids (e.g., alucones and titanicones)—unlocking unprecedented interfacial energetics mastery and mechanical compliance that decisively vanquish stability and charge-imbalance bottlenecks plaguing next-generation displays. Through rigorous conceptual demarcation between true ALD (vapor-phase and self-limiting) and related modifications (silylation, liquid-phase cross-linking, and vapor-phase infiltration), this mechanistically crystalline synthesis charts an interface-by-design roadmap propelling SNC-LEDs toward display-grade manufacturability, rearchitecting optoelectronics for flexible augmented reality (AR)/virtual reality (VR) displays, wearable ecosystems, and energy-efficient lighting.