Quantum dots having composition gradient shell structure and manufacturing method thereof

Abstract

Provided are quantum dots having a gradual composition gradient shell structure which have an improvedluminous efficiency and optical stability, and a method of manufacturing the quantum dots in a short amount of time at low cost. In the method, the quantum dots can be manufactured in a short amount of time at low cost using a reactivity difference between semiconductor precursors, unlike in uneconomical and inefficient conventional methods where shells areformed after forming cores and performing cleaning and redispersion processes. Also, formation of the cores is followed by formation of shells having a composition gradient. Thus, even if the shells are formed to a large thickness, the lattice mismatch between cores and shells is relieved. Furthermore, on the basis of the funneling concept, electrons and holes generated in the shells are transferred to the cores to emit light, thereby obtaining a high luminous efficiency of 80% or more. The quantum dot structure is not limited to Group II-IV semiconductor quantum dots but can be applied to other semiconductors quantum dots, such as Group III-V semiconductors quantum dots and Group IV-IV semiconductors quantum dots. Also, the manufacturing method can be utilized in the development of semiconductor quantum dots having different physical properties, and in various other fields.

Description

TECHNICAL FIELD[0001]The present invention relates to quantum dots having a gradual composition gradient shell structure and a method of manufacturing the same, and more particularly, quantum dots which have improved luminous efficiency and optical stability owing to a gradual composition gradient shell structure, and a method of manufacturing the same.BACKGROUND ART[0002]Conventionally, quantum dots have been manufactured using a dry chemical process, specifically, by inducing lattice mismatch between a substrate prepared in a vacuum and a layer deposited using a metal organic chemical vapor deposition (MOCVD) process. In this case, although nanoparticles may be formed and arranged on the substrate, expensive equipments are required. And it is also difficult to produce large quantities of quantum dots with a uniform size through conventional semiconductor fabrication methods. In order to solve these problems, a wet chemical process for synthesizing quantum dots with a uniform size ...

AI Technical Summary

Benefits of technology

[0016]According to the present invention, quantum dots can be manufactured in a short amount of time at low cost using a difference in reactivity between semiconductor precursors, unlike in uneconomical and inefficient conventional methods where shells are formed after forming cores through performing consecutive cleaning and redispersion processes. Also, according to the present invention, formation of cores is spontaneously followed by formation of shells having a composition gradient. Thus, even if shells are formed to a large thickness, the lattice mismatch between core and shell does not occur, unlike in conventional core-shell quantum dots. Furthermore, the funnel concept is applied to the present invention, so that electrons and holes absorbed in the shells are transferred to the cores to emit light, thereby a high luminous efficiency of 80% or higher is obtained. Moreover, the use of a surfactant can be minimized to facilitate a subsequent cleaning process, and the surfaces of synthesized quantum dots can be easily substituted, so that the quantum dots can be applied in different environments. As described above, the present invention provides new quantum dots having cores and shells with a gradual composition gradient, which can be applied to not only Group II-IV semiconductor quantum dots but also other semi-conductor quantum dots, such as Group III-V semiconductor quantum dots and Group IV-IV semiconductor quantum dots, and can be utilized in the development of semi-conductor quantum dots having different physical properties and in various other fields.

Problems solved by technology

In this case, although nanoparticles may be formed and arranged on the substrate, expensive equipments are required.

And it is also difficult to produce large quantities of quantum dots with a uniform size through conventional semiconductor fabrication methods.

However, in conventional core-shell quantum dots, when a thick shell is formed, an interface between the core and shell of the quantum dot becomes unstable due to the lattice mismatch between a core semiconductor material and a shell semiconductor material, thereby causes formation of defects which lower quantum efficiency of quantum dots.

Therefore the conventional core-shell quantum dots have limitations in luminous efficiency, optical stability, and environmental stability.

However, the manufacture of conventional core-multishell quantum dots involves complicated synthetic processes.

Also, during the sequential purification steps, some quantum dots and nonreacted precursors are removed too, which is counterproductive.

Furthermore, in quantum dots having a stacked shell structure obtained according to the synthesis process described above, only excitons generated in quantum-dot cores are used, while excitons generated in quantum-dot shells do not contribute to light emission, which limits luminous efficiency of quantum dots.

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