Nonthermalized Multiple Localized States Enable Efficient and Stable White-Light-Emitting Quantum Dots

Broadband emission from single quantum dot (QD) inherently relies on localized states that are conventionally regarded as nonradiative trap manifolds and suffer from low synthetic reproducibility. Here we show that photogenerated holes in a AgInxGa1-xS2/ZnS core/shell QD can be controllably partitioned into two parallel, kinetically isolated, and nonthermalized localized states, each of which then radiatively recombines with the delocalized electron with distinct formation and recombination kinetics. The high-energy and low-energy photoluminescence (PL) peaks are related to a small-polaron-like state in the core and a manifold of trap states near the core-shell boundary, respectively. The nonequilibrated dual-state architecture yields composition-tunable and ultrabroad emission with a PL full width at half maximum (fwhm) of 120-130 nm, near-unity quantum yield (QY), negligible Urbach tail, and robust operation under thermal and optical stress. Integrated with a blue GaN chip, a single type of QD produces efficient and stable warm-white light with a wall-plug efficiency as ∼150 lm W-1 and an electron-to-photon QY > 50%. Our results indicate localized states should be revisited as a valid paradigm for optoelectronic QD materials.