Photoluminescence from PbS QDs and PbS/CdS core/shell QDs Mixed with As2S3 glass

Abstract

Colloidal quantum dots (QDs) prepared by chemical routes have bright and narrow bandwidth luminescence. Furthermore, it is easy to engineer the surfaces of colloidal QDs by fabricating core/shell structures to enhance emission efficiency. PbS QDs have large Bohr radius ~ 18nm which provides strong confinement effect. In addition PbS semiconductor has a bulk bandgap of 0.41 eV. As a result PbS QDs possess bright and stable emission in near-infrared region (NIR). Emission efficiency of PbS QDs can also be improved by fabricating PbS/CdS core/shell QDs. Chalcogenide glasses are transparent to near-infrared up to mid-infrared light. Arsenic trisulfide (As2S3) glasses have high refractive index, high non-linear optical properties, low melting point and are easy to form fibers. It appears that chalcogenide glasses can provide excellent host matrices for IR-emitting QDs such as PbS QDs and PbS/CdS core/shell QDs. In this work, PbS QDs and PbS/CdS core/shell QDs were integrated into As2S3 glasses to obtain composites in bulk forms. We investigated photoluminescence of PbS QDs and PbS/CdS core/shell QDs in those composites. Compared to bare PbS QDs only, PbS/CdS core/shell QDs demonstrate enhancement in photoluminescence efficiency.