MoS2 quantum dots for photovoltaic device applications

Abstract

This work reports excellent blue downconversion photoluminescence and greenish-yellow upconversion photoluminescence emission of MoS2 QDs prepared by a simple and cost effective method called liquid phase exfoliation by magnetic stirring (LPEMS). MoS2 quantum dots (QDs) were prepared by liquid exfoliation of bulk MoS2 powder in ethanol. 1 g of bulk MoS2 powder was dispersed in 50 ml ethanol and subjected to magnetic stirring at 1000 rpm for 6 h. MoS2 QD dispersion was separated from the bulk by centrifuging at 5000 rpm for 10 min. MoS2 QDs of size 2-15 nm were observed by DLS experiment corresponding to different gate delay time. Particles sizes were also confirmed by TEM. Absorption spectroscopic studies indicate the QD optical transition peak centered at 308 nm. XRD of bulk MoS2 was recorded and confirmed the highly crystalline nature of MoS2 bulk crystals. The crystalline nature of MoS2 QDs was studied by selective area diffraction (SAED) pattern. The prepared QD solution showed excellent photon upconversion photoluminescence centered at 563 nm on excitation at 690-715 nm and blue downconversion photoluminescence centered at 418-446 nm on excitation at 280-320 nm. The photoluminescence upconversion and downconversion property of luminescent MoS2 QDs produced by this method can be applied in optoelectronic devices like solar cells.