Photo-stability and time-resolved photoluminescence study of colloidal CdSe/ZnS quantum dots passivated in Al{sub 2}O{sub 3} using atomic layer deposition

Journal Article · Sun Aug 28 00:00:00 EDT 2016 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4961425· OSTI ID:22598872

Cheng, Chih-Yi ^[1]; Mao, Ming-Hua ^[1]

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1. Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei 10617, Taiwan (China)

We report photo-stability enhancement of colloidal CdSe/ZnS quantum dots (QDs) passivated in Al{sub 2}O{sub 3} thin film using the atomic layer deposition (ALD) technique. 62% of the original peak photoluminescence (PL) intensity remained after ALD. The photo-oxidation and photo-induced fluorescence enhancement effects of both the unpassivated and passivated QDs were studied under various conditions, including different excitation sources, power densities, and environment. The unpassivated QDs showed rapid PL degradation under high excitation due to strong photo-oxidation in air while the PL intensity of Al{sub 2}O{sub 3} passivated QDs was found to remain stable. Furthermore, recombination dynamics of the unpassivated and passivated QDs were investigated by time-resolved measurements. The average lifetime of the unpassivated QDs decreases with laser irradiation time due to photo-oxidation. Photo-oxidation creates surface defects which reduces the QD emission intensity and enhances the non-radiative recombination rate. From the comparison of PL decay profiles of the unpassivated and passivated QDs, photo-oxidation-induced surface defects unexpectedly also reduce the radiative recombination rate. The ALD passivation of Al{sub 2}O{sub 3} protects QDs from photo-oxidation and therefore avoids the reduction of radiative recombination rate. Our experimental results demonstrated that passivation of colloidal QDs by ALD is a promising method to well encapsulate QDs to prevent gas permeation and to enhance photo-stability, including the PL intensity and carrier lifetime in air. This is essential for the applications of colloidal QDs in light-emitting devices.

• OSTI ID: 22598872
• Journal Information: Journal of Applied Physics, Vol. 120, Issue 8; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
AIR
ALUMINIUM OXIDES
CADMIUM SELENIDES
CARRIER LIFETIME
COMPARATIVE EVALUATIONS
EXCITATION
FLUORESCENCE
LASER RADIATION
LAYERS
LIGHT EMITTING DIODES
OXIDATION
PHOTOLUMINESCENCE
POWER DENSITY
QUANTUM DOTS
RECOMBINATION
STABILITY
SURFACES
THIN FILMS
TIME RESOLUTION
ZINC SULFIDES