Facile synthesis of large-Stokes-shift giant CdHgSe/CdHgSeS near-infrared quantum dots via chlorine-mediated Ostwald ripening

Abstract

Giant core/shell quantum dots (GQDs) offer advantages for optoelectronics, including suppressed blinking and reduced Auger recombination, yet thick-shell growth often requires laborious successive ion layer adsorption and reaction (SILAR) cycles. Here we demonstrate a chlorine-mediated controlled Ostwald ripening strategy that transforms NIR-emitting CdHgSe/CdS core/shell seed QDs into giant CdHgSe/CdHgSeS core/gradient-shell QDs in a single post-synthetic step. Seed QDs are prepared by growing a thin (similar to 1.6-monolayer) CdS shell on CdHgSe alloy cores. Injection of CHCl3 at 240 degrees C triggers rapid ripening, in which most seeds dissolve while a minor population grows into GQDs. During ripening, the band-edge absorption feature is strongly attenuated and absorption below similar to 610 nm increases markedly, whereas NIR emission remains centered near similar to 900 nm, yielding a large effective Stokes shift that can mitigate reabsorption in luminescent solar concentrators. HAADF-STEM/EDS and XRD support a compositionally graded shell, while mass spectrometry and numerical simulations are consistent with chlorine-modified surface chemistry and altered monomer solubility/surface tension that accelerate ripening. As a proof of concept, embedding the GQDs in PMMA affords a transparent luminescent solar concentrator prototype with retained NIR emission and favorable spectral overlap with silicon photovoltaics.