Fig. 1. The corresponding challenges of QDs. (I) Non-radiative recombination corresponding to photoluminance decay. (Ⅱ) High specific surface area corresponding to degradation and failure. (Ⅲ) Long chain ligands corresponding to poor carrier transport. (Ⅳ) Interfacial carrier accumulation and recombination corresponding to heat and efficiency roll-off.

Fig. 2. (a) PLQY value variation of QDs with TMA treatment time⁷⁵. (b) Reaction schematic of TMA with QDs surface⁷⁵. (c) PL lifetimes of QDs thin films before and after 20 cycles of alumina deposition⁶⁹. (d) XPS spectra of Zn for QDs thin film before and after one cycle of alumina and Al after one cycle of alumina⁶⁹. Figure reproduced from: (a, b) ref.⁷⁵, Creative Commons Attribution 2.0 International License; (c, d) ref.⁶⁹, American Chemical Society.

Fig. 3. (a) Cross-sectional TEM structure characterization and optical absorption spectra stability test before and after ALD treatment⁷⁴. (b) EELS color-coded elemental intensity maps of Al and Br, CsPbBr₃ QD/AlO_x nanocomposites PL properties over 45 days of storage in ambient conditions and after 1 h of soaking in water⁷⁰. Figure reproduced from: (a) ref.⁷⁴, American Chemical Society; (b) ref.⁷⁰, John Wiley and Sons.

Fig. 4. (a) Schematic of device architecture, FET electron mobility (black) and threshold voltage (blue) as a function of time stored and operated in air⁸⁶. (b) TEM image of device structure and the relative power conversion efficiency (PCE) over time⁸⁴. Figure reproduced from: (a) ref.⁸⁶, American Chemical Society; (b) ref.⁸⁴, AIP Publishing.

Fig. 5. (a) FTIR spectra of ALD-coated and uncoated thin films comprised of ZnO nanocrystals⁷⁶. (b) XPS scans for Pb 4f and Al 2p of the Al_xO_y-PbS film⁷⁸. (c) Ligands exchange and ALD infilling schematic resulting in barrier width and height reduce⁵⁵. Figure reproduced from: (a) ref.⁷⁶, American Chemical Society; (b) ref.⁷⁸, AIP Publishing; (c) ref.⁵⁵, American Chemical Society.

Fig. 6. (a) Schematic of barrier layer configurations available in quantum dot-sensitized solar cells. Comparison of device efficiency and dark current onset for TiO₂/Al₂O₃/QD and TiO₂/QD/Al₂O₃ configurations under 1 sun of illumination with varying ALD cycles of Al₂O₃⁸². (b) Band energy level diagram of each material in QLED. Current density of electron only device without and with Al₂O₃ interlayers, and hole only device. Device lifetime of QLEDs without and with Al₂O₃ interlayer⁶³. Figure reproduced from: (a) ref.⁸², American Chemical Society; (b) ref.⁶³, Creative Commons Attribution 3.0 International License.

Fig. 7. (a) Schematic diagram of the ALD interface passivating mechanism⁶¹. (b) EDS mappings obtained after device operation for QLEDs without and with an Al₂O₃ barrier layer⁶¹. Figure reproduced from ref.⁶¹, American Chemical Society.

Table 1. Summary of ALD systems reported in literature for applications in QDs and QDs based devices