Cd-free photoluminescent composites based on the ternary chalcogenides quantum dots

Abstract

Ternary chalcogenides quantum dots (QDs) are attractive light-converting materials owing to the absence of highly toxic metals (Cd), which are present in currently used QDs. Besides environmental friendliness, they possess broad, composition-tunable emission peaks with long photoluminescence lifetime, in a wide spectral range, which enables their usage as down-converting luminophors for light-emitting devices. Albeit, to improve QDs stability against the environment, as well as to widen an area of their possible applications, solid-state composites with incorporated QDs are preferable. AgInS2 QDs are one of the most prominent members of ternary chalcogenides, which can be synthesized easily. Thus, pristine QDs and QDs with ZnS shell were synthesized and embedded into the CaCO3 matrix. Copper doping can significantly expand the spectral window of AgInS2 QDs to red and NIR regions. Thus we researched Cu alloying with pristine AgInS2 quantum dots by the same means. The impact of the encapsulation on QDs optical properties was investigated using photoluminescence (PL) spectroscopy at ambient and cryogenic temperatures. We observed that QDs-matrix composites show PL in a broad spectral range (550–730 nm). Overall the CaCO3 matrix maintains original PL of incorporated QDs. Insignificant red shifts of PL peaks, especially in the case of Cu-containing QDs are probably caused by the interaction with CaCO3 material. During cryogenic PL measurements (10–300 K) we revealed that generally Cu alloying dramatically suppress AgInS2 QDs thermosensitivity. Copper doping of AgInS2 QDs increases their photostability by trapping of charge carriers at Cu clusters.