High efficiency luminescence from PbS quantum dots embedded glasses for near-infrared light emitting diodes

Abstract

PbS quantum dots (QDs) embedded glasses have been investigated for decades, but their applications are limited to the color filters and saturable absorbers for laser pulse generation so far, mainly due to the low photoluminescence quantum yield (PL QY) induced by the surface defects. Here, by increasing the sulfur to lead molar ratio in the glasses, surface defects of PbS QDs can be partially passivated and the fast trapping of charge carriers is reduced. As a result, PL QY of PbS QDs embedded glasses increases with larger sulfur to lead molar ratio, and PL QY as high as 46.9% is achieved. The improved PL QY along with good thermal and photo-stability makes the PbS QDs embedded glasses promising for near-infrared light generation. By integrating the PbS QDs embedded glass slab with light emitting diode (LED) chip, NIR LEDs with external quantum efficiency of 4.47% (@ ∼1.4 μm) with full width at half maximum larger than 140 nm are realized. Using this approach, it is also versatile to fabricate high-performance and broadband NIR LEDs with PbS QDs embedded glasses as light converters.