Spectral Narrowing of Ag–In–Ga–S Nanocrystals Enabled by Component Engineering

I–III–VI group semiconductor nanocrystals (NCs) with narrow-bandwidth emission have emerged as promising candidates for display technologies due to their tunable emission wavelength and eco-friendly composition. Herein, Ga-rich Ag–In–Ga–S (AIGS) NCs exhibited a narrow photoluminescence emission with a full width at half maximum (fwhm) of 29 nm, which was derived from In-rich Ag–In–Ga–S NCs with an fwhm of 113 nm via a cation exchange strategy. The evolution process was studied systematically using steady- and transient-state spectroscopic techniques, revealing that the narrow photoluminescence (PL) bandwidth primarily originated from free-to-bound radiative recombination. The result was consistent with first-principles calculations. Furthermore, the electroluminescent devices based on AIGS NCs showed a record narrow electroluminescent bandwidth of less than 30 nm, and the maximum external quantum efficiency (EQE) could reach up to 1.2%.