Heterostructure Design of Zn Chalcogenide Shell on Ga-rich In_1-XGa_XAs Quantum Dots

Colloidal quantum dots (QDs) have been expanding their applications from visible to near infrared (NIR) wavelengths. However, efficient NIR-emitting QDs without heavy metal have very limited material candidates. Here, Ga-rich In_1-XGa_XAs with zinc chalcogenide shell is suggested as a candidate for NIR emitters. Based on the development of molten salt chemistry, spherical In_1-XGa_XAs QDs with Ga contents up to 85 % were synthesized, which showed highly crystalline structure based on Raman and XRD analyses. Zinc selenide shell with different morphologies were grown on In_1-XGa_XAs QDs by controlling Zn precursor. Considering lattice mismatch and band alignment, a ZnS shell was adopted, resulting in a photoluminescence quantum yield (PL QY) of about 50 %. Based on spectroscopic analysis, which compares PL decay and transient absorption (TA) dynamics, we revealed that electron trapping is the major reason for efficiency loss, which offers a heterostructure design plan to realize efficient NIR-emitting In_1-XGa_XAs QD.