Red green blue emissive lead sulfide quantum dots: heterogeneous synthesis and applications

Visible emission colloidal quantum dots (QDs) have shown promise in optical and optoelectronic applications. These QDs are typically composed of relatively expensive elements in the form of indium, cadmium, and gallium since alternative candidate materials exhibiting similar properties are yet to be realized. Herein, for the first time, we report red green blue (RGB) photoluminescences with quantum yields of 18% from earth-abundant lead sulfide (PbS) QDs. The visible emissive property is mainly attributed to a high degree of crystallinity even for the extremely small QD sizes (1-3 nm), which is realized by employing a heterogeneous reaction methodology at high growth temperatures (>170 °C). We demonstrate that the proposed heterogeneous synthetic method can be extended to the synthesis of other metal chalcogenide QDs, such as zinc sulfide and zinc selenide, which are promising for future industrial applications. More importantly, benefiting from the enlarged band gaps, the as-prepared PbS solar cells show an impressive open circuit voltage (∼0.8 V) beyond that reported to date.