Narrow red-emitting InP quantum dots with 38 nm FWHM: mechanistic insights into the role of In(i)Cl precursors

Abstract

Indium phosphide quantum dots (InP QDs) have garnered significant attention as promising alternatives to cadmium-based QDs due to their low toxicity and high photoluminescence efficiency. However, the full width at half maximum (FWHM) of red-emitting InP QDs synthesized via aminophosphine-based methods remains approximately 45 nm, significantly limiting their application in high color gamut display technologies. In this study, we used indium(I) chloride (In(I)Cl) and tris(dimethylamino)phosphine (P(DMA)₃) as precursors to synthesize red-emitting InP QDs, combined with HF etching to significantly enhance their optical performance. The resulting InP QDs exhibited a narrow emission spectrum with a FWHM of 38 nm, the narrowest reported value for red-emitting InP QDs synthesized using aminophosphine precursors, approaching the FWHM of red QDs synthesized from silicon-based phosphines. Comprehensive kinetic studies of both reaction and growth processes revealed that the In(I)Cl precursor demonstrates substantially reduced reactivity. In(I)Cl initially undergoes disproportionation to form In(III) species prior to participating in transamination reactions. This unique reaction not only reduces the overall reaction rate but also enables a sustained and stable supply of In monomers, thereby prolonging the growth period and ultimately achieving a narrower FWHM. Low-temperature photoluminescence spectroscopy and X-ray photoelectron spectroscopy revealed that HF etching facilitates surface passivation by forming InF₃ as a Z-type ligand, while HF effectively eliminates surface dangling bonds and decomposes polyphosphate impurities, resulting in core-only InP QDs with an exceptional quantum yield (PLQY) of 80%. This study provides valuable insights and guidance for future research and applications of InP systems.