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Enhanced thermal stability of InP quantum dots coated with Al-doped ZnS shell
- Enhanced thermal stability of InP quantum dots coated with Al-doped ZnS shell
- Koh, Sungjun; Lee, Hyeonjun; Lee, Taemin; Park, Kyoungwon; Kim, Woo-Jae; Lee, Doh C.
- Ewha Authors
- Issue Date
- Journal Title
- JOURNAL OF CHEMICAL PHYSICS
- JOURNAL OF CHEMICAL PHYSICS vol. 151, no. 14
- AMER INST PHYSICS
- SCIE; SCOPUS
- Document Type
- Colloidal InP quantum dots (QDs) have attracted a surge of interest as environmentally friendly light-emitters in downconversion liquid crystal displays and light-emitting diodes (LEDs). A ZnS shell on InP-based core QDs has helped achieve high photoluminescence (PL) quantum yield (QY) and stability. Yet, due to the difficulty in the growth of a thick ZnS shell without crystalline defects, InP-based core/shell QDs show inferior stability against QY drop compared to Cd chalcogenide precedents, e.g., CdSe/CdS core/thick-shell QDs. In this work, we demonstrate the synthesis of InP-based core/shell QDs coated with an Al-doped ZnS outer shell. QDs with an Al-doped shell exhibit remarkable improvement in thermal and air stability even when the shell thickness is below 2 nm, while the absorption and PL spectra, size, and crystal structure are nearly the same as the case of QDs with a pristine ZnS shell. X-ray photoelectron spectroscopy reveals that Al3+ in Al-doped QDs forms an Al-oxide layer at elevated temperature under ambient atmosphere. The as-formed Al-oxide layer blocks the access of external oxidative species penetrating into QDs and prevents QDs from oxidative degradation. We also trace the chemical pathway of the incorporation of Al3+ into ZnS lattice during the shell growth. Furthermore, we fabricate QD-LEDs using Al-doped and undoped QDs and compare the optoelectronic characteristics and stability.
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