Abstract
Quantum-dot (QD) light-emitting devices (QLEDs) have been attracting considerable attention owing to the unique properties of process, which can control the emission wavelength by controlling the particle size, narrow emission bandwidth, and high brightness. Although there have been rapid advances in terms of luminance and efficiency improvements, the long-term device stability is limited by the low chemical stability and photostability of the QDs against moisture and air. In this study, we report a simple method, which can for enhance the long-term stability of QLEDs against oxidation by inserting Al into the shells of CdSe/ZnS QDs. The Al coated on the ZnS shell of QDs act as a protective layer with Al2O3 owing to photo-oxidation, which can prevents the photodegradation of QD with prolonged irradiation and stabilize the device during a long-term operation. The QLEDs fabricated using CdSe/ZnS/Al QDs exhibited a maximum luminance of 57,580 cd/m2 and current efficiency of 5.8 cd/A, which are significantly more than 1.6 times greater than that of CdSe/ZnS QDs. Moreover, the lifetimes of the CdSe/ZnS/Al-QD-based QLEDs were significantly improved owing to the self-passivation at the QD surfaces.
Highlights
Solution-synthesized quantum dots (QDs) have been intensively studied owing to their inherent luminescent characteristics, narrow emission spectral characteristics through particle size control, and high luminescent efficiency with solution processing[1]
It is worth nothing that no significant difference in ultraviolet (UV)-visible absorption spectrum was observed between the QDs with/without the Al shells
These results indicate that there is no significant difference in the energy gap (Eg) between QDs with and without Al shells
Summary
Solution-synthesized quantum dots (QDs) have been intensively studied owing to their inherent luminescent characteristics, narrow emission spectral characteristics through particle size control, and high luminescent efficiency with solution processing[1]. The groups of Yang and Li proposed a method for doping ZnS shells with Al for QD production that is solution processable and effective self-passivation[17,18] These studies showed that, upon light irradiation, the Al doped in the ZnS shell became photo-oxidized into Al2O3, which acted as a protective layer and prevented photodegradation of the QDs upon a prolonged irradiation. These studies reported a substantial enhancement in the photostability, the complex fabrication process of the individual core and shell, as well as the Al doping, required a long fabrication time. In order to evaluate the performances of the Al-QLEDs, we fabricated solution-processable QLEDs by employing a modification of previously reported methods[19,20]
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