High-Power Genuine Ultraviolet Light-Emitting Diodes Based On Colloidal Nanocrystal Quantum Dots

• Published in: Nano letters Vol. 15; no. 6; pp. 3793 - 3799
• Main Authors: Kwak, Jeonghun, Lim, Jaehoon, Park, Myeongjin, Lee, Seonghoon, Char, Kookheon, Lee, Changhee
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 10.06.2015
• Subjects: Cadmium Compounds - chemistry; Colloids; Nanoparticles - chemistry; Quantum Dots - chemistry; Sulfides - chemistry; Ultraviolet Rays; Zinc Compounds - chemistry; quantum dots; quantum dot light-emitting diodes; ultraviolet light-emitting diodes; ultraviolet
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/acs.nanolett.5b00392

Thin-film ultraviolet (UV) light-emitting diodes (LEDs) with emission wavelengths below 400 nm are emerging as promising light sources for various purposes, from our daily lives to industrial applications. However, current thin-film UV-emitting devices radiate not only UV light but also visible light. Here, we introduce genuine UV-emitting colloidal nanocrystal quantum dot (NQD) LEDs (QLEDs) using precisely controlled NQDs consisting of a 2.5-nm-sized CdZnS ternary core and a ZnS shell. The effective core size is further reduced during the shell growth via the atomic diffusion of interior Cd atoms to the exterior ZnS shell, compensating for the photoluminescence red shift. This design enables us to develop CdZnS@ZnS UV QLEDs with pure UV emission and minimal parasitic peaks. The irradiance is as high as 2.0–13.9 mW cm–2 at the peak wavelengths of 377–390 nm, several orders of magnitude higher than that of other thin-film UV LEDs.