Chemical physics of surface reconstruction and defect passivation in InP quantum dots: Thermodynamic mechanisms, electronic structure evolution, and implications for high-performance optoelectronics

Indium phosphide (InP) quantum dots (QDs) have emerged as promising cadmium-free nanomaterials for advanced optoelectronic applications owing to their tunable optical properties and improved environmental compatibility. However, their performance remains limited by complex surface defects arising from covalent In–P bonding, stoichiometric imbalance, facet-dependent atomic reconstruction, and dynamic ligand interactions. This review provides a chemical-physics perspective on the mechanisms governing surface reconstruction, defect formation, and passivation in InP QDs. The atomistic origins of dangling bonds, surface electronic states, and composition-dependent band-structure modifications are examined in relation to carrier trapping and non-radiative recombination. Particular attention is given to the thermodynamic and kinetic principles controlling ligand exchange equilibria, ligand-shell cooperativity, and surface reactivity, which collectively determine defect stability and surface energetics. Recent advances in halide-mediated passivation, metal-assisted coordination engineering, and simultaneous neutralization of indium- and phosphorus-related dangling bonds are critically evaluated as effective strategies for suppressing trap states and improving photoluminescence efficiency. Environmental degradation pathways, including oxidation, hydrolysis, and ligand desorption, are also discussed. Finally, emerging predictive and application-oriented surface-engineering frameworks integrating thermodynamic modeling, dynamic surface equilibria, and data-driven materials design are highlighted as pathways toward highly efficient and stable InP QD-based optoelectronic devices.

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