After the discovery of semi-metallic graphene, layered materials such as hexagonal Boron Nitride (h-BN) and molybdenum disulphide (MoS2) have attracted a lot of attention. For example, h-BN sheets have become the indispensable underlayers for two dimensional (2D) devices with high electron mobility despite being electrical insulating. On the other hand, the indirect to direct band gap conversion in MoS2 is due to the quantum confinement effect along the thickness axis of the 2D materials. Here, we present the synthesis and properties of h-BN and MoS2 quantum dots (QDs) by creating quantum confinement in axes perpendicular to the thickness axis. These QDs offer unique and broad spectra absorption bands for effective photoelectron generation for use in QD-sensitized photovoltaic devices.
A top-down approach was employed to convert h-BN and MoS2 particles into QDs by using sonication, and solvo-thermal in Dimethylformamide (DMF). The MoS2 are 2-40 nm in dimension, while the BN QDs are 2-8 nm in dimension. We show that the fluorescent emission from these polydisperse QDs are excitation wavelength dependent. These MoS2 QDs could absorb a wide spectrum range of light from 320-520 nm to produce fluorescence emission from 385-569 nm. The h-BN QDs can absorb a broader spectra from 300-580 nm with fluorescence emission of 380-620 nm. The broad absorption wavelength range of these QDs would meet the peak of solar irradiation spectrum to enable effective production of photoelectrons from the sun for the applications of photovoltaic devices. Detailed of these results will be discussed in the meeting.