Overcoating inorganic quantum dot and method for preparing the same

Abstract

An overcoating inorganic quantum dot and a method for preparing the same are provided. The overcoating inorganic quantum dot includes at least one perovskite quantum dot with an oxide overcoat. The method includes forming the perovskite quantum dots, and overcoating an oxide overcoat on the perovskite quantum dots.

Claims

1. An overcoating inorganic quantum dot, comprising: a plurality of perovskite quantum dots being contained in a single oxide overcoat, wherein the oxide overcoat is In.sub.2O.sub.3.

2. The overcoating inorganic quantum dot according to claim 1, wherein the perovskite quantum dot is CsPb(Cl.sub.xBr.sub.1-x-yI.sub.y).sub.3, x=0-1, y=0-1, and x+y1.

3. The overcoating inorganic quantum dot according to claim 1, wherein the overcoating inorganic quantum dot has an average particle size of 8-100 nm.

4. A method for preparing an overcoating inorganic quantum dot, comprising: forming a plurality of perovskite quantum dots; and adding a reactant of indium(III) acetate and oleylamine to overcoat an oxide overcoat on at least one of the perovskite quantum dots for forming the overcoating inorganic quantum dot, wherein the oxide overcoat is In.sub.2O.sub.3.

5. The method according to claim 4, wherein the perovskite quantum dot is CsPb(Cl.sub.xBr.sub.1-x-yI.sub.y).sub.3, x=0-1, and y=0-1.

6. The method according to claim 4, further comprising purifying the overcoating inorganic quantum dot after overcoating the oxide overcoat.

7. The method according to claim 4, further comprising preparing a Cs-Oleate precursor before forming the plurality of perovskite quantum dots.

8. The method according to claim 7, wherein forming the plurality of perovskite quantum dots comprises using the Cs-Oleate precursor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

(2) FIG. 1 is a schematic diagram illustrating a specific embodiment of preparing the overcoating inorganic quantum dot in accordance with this invention.

(3) FIG. 2A and FIG. 2B are transmission electron microscopy (TEM) photographs of experimental example in different magnification according to this invention.

(4) FIG. 3 is an emission spectrum of experimental example and comparative example.

(5) FIG. 4 is XRD curves of experimental example and comparative example with standard CsPbBr.sub.3 and In.sub.2O.sub.3.

(6) FIG. 5A shows the thermal stability of comparative example.

(7) FIG. 5B shows the thermal stability of experimental example in accordance with this invention.

DESCRIPTION OF THE EMBODIMENTS

(8) Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.

(9) FIG. 1 is a schematic diagram illustrating a specific embodiment of preparing the overcoating inorganic quantum dot in accordance with this invention.

(10) With reference to FIG. 1, the overcoating inorganic quantum dot is a plurality of perovskite quantum dots 100 with an oxide overcoat 102, wherein the overcoating inorganic quantum dot, for instance, has an average particle size D of 8-100 nm; preferably 8-80 nm. In one embodiment, the perovskite quantum dot 100 is CsPb(Cl.sub.xBr.sub.1-x-yI.sub.y).sub.3, wherein x=0-1, y=0-1, and x+y1. In one embodiment, the oxide overcoat 102 is metal oxide such as In.sub.2O.sub.3.

(11) In FIG. 1, there are three perovskite quantum dots 100 contained in the oxide overcoat 102, but this invention is not limited thereto. In other embodiment, only one perovskite quantum dots 100 may be included in the oxide overcoat 102. In yet another embodiment, a large number of perovskite quantum dots 100 may be included in the oxide overcoat 102.

(12) The preparation of the overcoating inorganic quantum dot includes forming perovskite quantum dots 100 and then overcoating an oxide overcoat 102 on the perovskite quantum dots 100 as shown in FIG. 1. In one embodiment, before forming the perovskite quantum dots 100, a Cs-Oleate precursor is prepared so as to use the Cs-Oleate precursor with the reactant of PbX.sub.2 (X represents Cl, Br, or I) and oleylamine for synthesizing the perovskite quantum dots 100. In one embodiment, the step of overcoating the oxide overcoat 102 may add a reactant of indium(III) acetate and oleylamine. After overcoating the oxide overcoat 102, a purifying is optionally performed on the overcoating inorganic quantum dot.

(13) The following describes experiments carried out in order to verify the effect of this invention. However, the scope of this invention is not limited to the following experiments.

Experimental Example: Synthesis of Overcoating Inorganic Quantum Dot

(14) Step a. Preparing a Cs-Oleate Precursor

(15) 0.814 g Cs.sub.2CO.sub.3 was mixed with 40 mL octadecene (ODE) and 2.5 mL oleic acid to react under 120 C. and vacuum condition for one hour, then the mixture was heated to 150 C. in N.sub.2 atmosphere until Cs.sub.2CO.sub.3 and ODE reacted completely to obtain the Cs-Oleate precursor.

(16) Step b. Preparing Precursor of In.sub.2O.sub.3

(17) 100 mg indium(III) acetate was reacted with 5 mL oleylamine in 120 C. for 30 min and kept in 120 C. in order to use as the precursor of In.sub.2O.sub.3.

(18) Step c. Synthesis of CsPbBr.sub.3 Quantum Dots

(19) 5 ml ODE and 0.188 mmol PbBr.sub.2 were mixed and then heated to 120 C. under vacuum for 1 hr. Thereafter, 0.5 mL oleylamine and 0.5 mL ODE were added to the mixture.

(20) After above reactant was dissolved completely, it was heated to 140-200 C. under N.sub.2 atmosphere. 0.4 mL of the Cs-Oleate precursor obtained in Step a was added into the reactant, and then the mixture was cooled down to 120 C. to obtain the suspension of CsPbBr.sub.3 quantum dots.

(21) Step d. Synthesis of the Overcoating Inorganic Quantum Dot

(22) The precursor of In.sub.2O.sub.3 obtained in Step b was added in to the suspension of CsPbBr.sub.3 in Step c. After one-hour reaction, this solution was cooled down in ice, and t-butanol was added into it (volume ratio=1:1) to purify the overcoating inorganic quantum dot.

(23) FIG. 2A and FIG. 2B are TEM photographs of the product of experimental example in different magnification. It is determined from FIG. 2A that lattice constant of the overcoating inorganic quantum dot is 5.6 and its grain size is around 10 nm. Furthermore, in FIG. 2B, it is shown that the particle size of the overcoating inorganic quantum dot is about tens of nanometer, and it is clear that a number of perovskite quantum dots (i.e. black points) is contained in single oxide overcoat (i.e. grey portion).

Comparative Example

(24) The Steps a and c of the experimental example were performed to prepare CsPbBr.sub.3 as comparative example.

(25) Detection

(26) The comparisons between experimental example and comparative example was as below.

(27) As shown in FIG. 3, the FWHM and emission wavelength of experimental example and comparative example are almost the same, and thus they are not distinguished each other in FIG. 3. The emission peak of experimental example is 514 nm, and the FWHM of experimental example is 18 nm. The emission peak of comparative example is 515 nm, and the FWHM of comparative example is 20 nm.

(28) FIG. 4 is XRD curves of experimental example and comparative example with standard CsPbBr.sub.3 and In.sub.2O.sub.3. In FIG. 4, the top spectrum is the XRD of standard CsPbBr.sub.3, and the bottom spectrum is the XRD of standard In.sub.2O.sub.3. The major peak for experimental example was contributed by In.sub.2O.sub.3, and thus the peak of CsPbBr.sub.3 was a little inconspicuous. The peak of CsPbBr.sub.3 in the experimental example shifted from 2=30.49 to 2=30.28.

(29) FIGS. 5A and 5B show comparison of the thermal stability of the experimental example and comparative example. The emission intensity of experimental example is improved from 35% (CsPbBr.sub.3 without In.sub.2O.sub.3 overcoat) to 65% after being heated under 100 C. for 10 mins. This is the evidence that the perovskite is overcoated by In.sub.2O.sub.3.

(30) In summary, according to this invention, the perovskite quantum dots have the oxide overcoat, and thus the thermal stability of the overcoating inorganic quantum dot is improved extremely. Moreover, the perovskite quantum dots and the oxide overcoat may be prepared under 300 C., and thus it may be useful to the massive production.

(31) It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.