Potential-landscape engineering via cation exchange for color-pure and stable Ag-(In,Ga)-S core/multishell nanocrystals

Abstract

The development of high-performance, non-toxic nanocrystals (NCs) is essential for next-generation optoelectronic applications, yet realizing both high color purity and long-term stability in silver-based chalcogenides remains a formidable challenge. This is largely hindered by the cation intermixing inherent in conventional heteroepitaxy with ZnE (E = Se, S), which often deteriorates spectral purity. Here, we report a core-multishell (CMS) architecture for Ag(In, Ga)S-2 (AIGS) NCs that yields stable and narrow-band emission through precise potential-landscape engineering. By initiating a surface-selective cation exchange (Ag+/Ga3+ to Zn2+) on a thick, Ag-deficient AgGaS2 (AGS) shell, we construct a ZnGa2S4 (ZGS) exterior layer that creates a substantial potential barrier (Delta E-g = 0.9 eV relative to AGS) for Type-I band alignment and a net outward dipole. This structure lowers the electronic energy levels by 0.12 eV and effectively decouples radiative recombination from surface-related trap states. Individual NC spectroscopy reveals a near-unity on-time fraction (97%) and suppressed photoluminescence (PL) blinking, while macroscopic assays demonstrate superior resistance to oxidative (T-90 > 200 hr) and electrochemical degradation. Finally, incorporating these C-MS NCs into LEDs yields colorpure electroluminescence (EL) identical to the intrinsic PL spectrum-a first for AIGS systems, free from defect-mediated broadening. Our findings provide a robust strategy for tailoring the electronic structure of multicomponent NCs, paving the way for their practical use in high-definition displays, lasers, and quantum information technologies.