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ACS Appl Mater Interfaces. 2018 Dec 12;10(49):42647-42656. doi: 10.1021/acsami.8b15212. Epub 2018 Nov 27.

Surface Engineering of Room Temperature-Grown Inorganic Perovskite Quantum Dots for Highly Efficient Inverted Light-Emitting Diodes.

Author information

1
Advanced Display Research Center (ADRC) and Department of Information Display , Kyung Hee University , 26, Kyungheedae-ro , Dongdaemun-gu, Seoul 02447 , South Korea.

Abstract

Inorganic cesium lead bromide quantum dots (CsPbBr3 QDs) are usually synthesized via a high-temperature process (hot injection, HI). This process is similar to that used for the synthesis of other semiconductor QDs (i.e., CdSe@ZnS), which limits their potential cost advantage. CsPbBr3 QDs can also be synthesized at room temperature (RT) in a low cost and easily scalable process, which, thus, is one of the greatest advantages of the CsPbBr3 QDs. However, light-emitting diodes (LEDs) fabricated using RT-QDs exhibit poor performance compared to those of HI-QDs. In fact, QDs are surrounded by insulating ligands to maintain their colloidal stability but these ligands need to be removed to obtain high-performance LEDs. Here, we show that ligand removal techniques used for HI-QDs are not sufficient in the case of RT-QDs. Additional ligand engineering and annealing steps are necessary to remove the excess of ligands from RT-QD films while preventing the coalescence of the QDs. The eventual surface defects induced by annealing can be healed by a subsequent photoactivation step. Moreover, the use of solution processable inorganic charge transport layers can reduce the fabrication costs of LEDs. We fabricated an inverted LED based on a metal oxide electron transport layer and a RT-QD emitting layer which exhibited a maximum current efficiency of 17.61 cd A-1 and a maximum luminance of 22‚ÄČ825 cd m-2.

KEYWORDS:

ligands assisted reprecipitation; ligands exchange; light emitting diodes; perovskite quantum dots; photo activation

PMID:
30419162
DOI:
10.1021/acsami.8b15212

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