PROCESS FOR SYNTHESIS OF B-SITE DOPED ABX3 PEROVSKITE NANOCRYSTALS

Abstract

The present invention relates to a process for the synthesis of B-site doped ABX.sub.3 perovskite nanocrystals. The process comprises the steps of loading non-halide precursors of A, B, and dopant in three neck flasks along with long chain acid and olefin, purging of the reaction mixture under heating, and finally injection of alkylammonium chloride stock solution in the reaction mixture at a desired temperature. Introducing transition metal such as Mn and other rare earths, etc., as dopants in the perovskite nanocrystals to induce a new optical window.

Claims

1. A process for preparation of D-doped ABX.sub.3 perovskite nanocrystals, the process comprising: (a) loading non-halide precursors of A, B and D in a three-neck flask along with a long chain acid and a linear alpha olefin solvent to form a reaction mixture; (b) purging the reaction mixture with an inert gas at a temperature in a range of 100-160 C. for 30 minutes; (c) injecting an alkylammonium halide solution in the reaction mixture at a temperature in a range of 80-200 C.; (d) annealing the reaction mixture for 5 seconds to 1 hour and cooling down naturally; and (e) precipitating the D-doped ABX.sub.3 nanocrystals.

2. The process as claimed in claim 1, wherein the non-halide precursors A and B are present in a ratio of 1:1.

3. The process as claimed in claim 1, wherein D is present in a range of 5-50 wt. % with respect to A and B.

4. The process as claimed in claim 1, wherein A is selected from cesium (Cs) and formamidinium (FA); B is lead (Pb); and X is selected from chlorine (Cl), bromine (Br) and iodine (I).

5. The process as claimed in claim 1, wherein D is selected from manganese (Mn), nickel (Ni), cobalt (Co), iron (Fe), magnesium (Mg), beryllium (Be), calcium (Ca), strontium (Sr), barium (Ba), bismuth (Bi), antimony (Sb), cerium (Ce), samarium (Sm), europium (Eu), terbium (Tb), dysprosium (Dy), erbium (Er), ytterbium (Yb), zinc (Zn), cadmium (Cd), thallium (Tl), tin (Sn).

6. The process as claimed in claim 1, wherein the non-halide precursor source is selected from carbonate, acetate, nitrate, acetylacetonate, oleate, undecylenate, myristate, laurate, or palmitate.

7. The process as claimed in claim 1, wherein the long chain acid is selected from oleic acid, undecylenic acid, dodecanoic acid, hexadecanoic acid, or hexadecanoic acid.

8. The process as claimed in claim 1, wherein the linear alpha olefin solvent is selected from 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, or 1-octadecene.

9. The process as claimed in claim 1, wherein the alkylammonium halide is selected from chloride or bromide or iodide salts of octylammonium, oleylammonium, dodecylammonium, dodecylamine, dihexylammonium, dioctylammonium, didecylammonium, or dioctdecylammonium.

10. The process as claimed in claim 1, wherein the process comprises preparation of D-doped AB.sup.1.sub.1-yB.sup.2.sub.yX.sub.3 perovskite nanocrystals, wherein B.sup.1 comprises silver (Ag), sodium (Na) and potassium (K); B.sub.2 comprises indium (In), bismuth (Bi) and antimony (Sb); and y=0 to 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] FIG. 1 relates to process flow diagram of the present invention.

[0032] FIG. 2 relates to UV-Vis absorbance spectra of Mn-doped CsPbCl.sub.3-xBr.sub.x nanocrystals.

[0033] FIG. 3 relates to PL spectra of Mn-doped CsPbCl.sub.3-xBr.sub.x nanocrystals.

[0034] FIG. 4 relates to PLE spectra Mn-doped CsPbCl.sub.3-xBr.sub.x nanocrystals.

[0035] FIG. 5 relates to Powder XRD Pattern of Mn-doped CsPbCl.sub.3-xBr.sub.x nanocrystals.

[0036] FIG. 6 relates to weight loss profile of the synthesized nanocrystals in thermogravimetric analysis.

DETAILED DESCRIPTION OF THE INVENTION

[0037] Those skilled in the art will be aware that the present disclosure is subject to variations and modifications other than those specifically described. It is to be understood that the present disclosure includes all such variations and modifications. The disclosure also includes all such steps of the process, features of the system, referred to or indicated in this specification, individually or collectively and all combinations of any or more of such steps or features.

Definitions

[0038] For convenience, before further description of the present disclosure, certain terms employed in the specification, and examples are collected here. These definitions should be read in the light of the remainder of the disclosure and understood as by a person of skill in the art. The terms used herein have their meanings recognized and known to those of skill in the art, however, for convenience and completeness, particular terms and their meanings are set forth below.

[0039] The articles a, an and the are used to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article.

[0040] The terms comprise and comprising are used in the inclusive, open sense, meaning that additional elements may be included. It is not intended to be construed as consists of only.

[0041] Throughout this specification, unless the context requires otherwise the word comprise, and variations such as comprises and comprising, will be understood to imply the inclusion of a stated element or step or group of element or steps but not the exclusion of any other element or step or group of element or steps.

[0042] The term including is used to mean including but not limited to. Including and including but not limited to are used interchangeably.

[0043] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the disclosure, the preferred methods, and materials are now described. All publications mentioned herein are incorporated herein by reference.

[0044] The present disclosure is not to be limited in scope by the specific embodiments described herein, which are intended for the purposes of exemplification only. Functionally equivalent products and processes are clearly within the scope of the disclosure, as described herein.

[0045] The present invention discloses a process for preparation of D-doped ABX.sub.3 perovskite nanocrystals or B-site doped ABX.sub.3 perovskite nanocrystals. The process comprises: [0046] (a) loading non-halide precursors of A, B and dopant (D) in a three-neck flask along with a long chain acid and a linear alpha olefin solvent to form a reaction mixture; [0047] (b) purging the reaction mixture with an inert gas at a temperature in a range of 100-160 C. for 10 to 60 minutes; [0048] (c) injecting an alkylammonium halide solution in the reaction mixture at a temperature in a range of 80-200 C.; [0049] (d) annealing the reaction mixture for 5 seconds to 1 hour and cooling down naturally; and [0050] (e) precipitating the D-doped ABX.sub.3 nanocrystals.

[0051] In another embodiment, the process further comprises preparation of D-doped AB.sup.1.sub.1-yB.sup.2.sub.yX.sub.3 perovskite nanocrystals, wherein B.sup.1 comprises silver (Ag), copper (Cu), indium (In), gold (Au), thalium (Tl), sodium (Na) and potassium (K); B.sub.2 comprises indium (In), bismuth (Bi) and antimony (Sb); and y=0 to 1.

[0052] In yet another embodiment, A is selected from caesium (Cs), methylammonium (MA) and formamidinium (FA); and B is lead (Pb). Further, X is selected from chlorine (Cl), bromine (Br) and iodine (I).

[0053] In another embodiment, dopant (D) is selected from manganese (Mn), nickel (Ni), cobalt (Co), copper (Cu), iron (Fe), magnesium (Mg), beryllium (Be), calcium (Ca), strontium (Sr), barium (Ba), bismuth (Bi), antimony (Sb), cerium (Ce), samarium (Sm), europium (Eu), terbium (Tb), dysprosium (Dy), erbium (Er), ytterbium (Yb), zinc (Zn), cadmium (Cd), thallium (Tl), tin (Sn). The dopant (D) comprises transition metal such as Mn, Ni, Fe, Cu etc. and rare earth metals such as Yb, Ce, La etc. and are introduced in perovskite nanocrystals to induce a new optical window and enhance stability.

[0054] In another embodiment, the non-halide precursor source is selected from carbonate, acetate, nitrate, acetylacetonate, oleate, undecylenate, myristate, laurate, or palmitate.

[0055] In another embodiment, the long chain acid is selected from oleic acid, undecylenic acid, dodecanoic acid, hexadecanoic acid, or hexadecanoic acid. The linear alpha olefin solvent is selected from 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, or 1-octadecene.

[0056] In another embodiment, the alkylammonium halide is selected from chloride or bromide or iodide salts of octylammonium, oleylammonium, dodecylammonium, dodecylamine, dihexylammonium, dioctylammonium, didecylammonium, or dioctdecylammonium. These alkylammonium halide act as a passivating agent and stabilizes these nanocrystals. Therefore, no immediate quenching of the reaction is required.

[0057] In yet another embodiment, the process includes no use of phosphine and no re-precipitation of lead precursor.

[0058] In yet another embodiment, the non-halide precursors A and B are taken preferably in the 1:1 ratio and Mn precursor ranges from 5 to 50 wt. % with respect to A or B.

[0059] In yet another embodiment, the non-halide precursors react with the long chain acids and generate respective carboxylates. These carboxylates are highly soluble in organic medium (1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, or 1-octadecene) and never precipitate out in the temperature range of 80-200 C.

[0060] In another embodiment, the invention can be extended to other doped perovskite materials such as D-doped ABCl.sub.3-xBr.sub.x (D=Mn, A=Cs, BPb, and x=1 to 3).

EXAMPLES

[0061] Having described the basic aspects of the present invention, the following non-limiting examples illustrate specific embodiments thereof. Those skilled in the art will appreciate that many modifications may be made in the invention without changing the essence of invention.

Example 1: Synthesis of Oleylammonium Chloride Stock Solution

[0062] In a typical synthesis, 40 ml of oleylamine was taken in a 100 ml 3-neck reaction flask placed in a heating mantel connected with a programmed temperature controller. One neck of the reaction flask was fitted with a temperature sensor, second neck was connected with an air-condenser, and the third neck was left open. Then 4 ml HCl (37% v/v) was injected in the reaction flask. Reaction of HCl with oleylamine results into a solid salt residue. To remove water from the system, reaction mixture was heated at 120 C. for 30 minutes. Then the third neck of the flask was closed with rubber septum and nitrogen was purged in the flask by a needle. Finally, the temperature was increased to 150 C., and the reaction mixture was heated further for 30 minutes. Then the reaction temperature was decreased to 100 C. and the resulting stock solution was collected under hot condition in an airtight syringe and stored in a deaerated 100 ml flask fitted with a screw type septum. On cooling down to room temperature, the stock solution was solidified. Solidified salt was melted at 80 C. before using it for the synthesis of nanocrystals.

Example 2: Synthesis of Oleylammonium Bromide Stock Solution

[0063] The synthesis of oleylammonium bromide was same as Example 1. To have same salt concentration like oleylammonium chloride, 5.1 ml HBr (47% v/v) was used instead of 4 ml HCl. Rest of the procedure remains same.

Example 3: Synthesis of Mn-Doped CsPbCl.SUB.3 .Nanocrystals

[0064] In a typical synthesis 0.2 mmol of Cs.sub.2CO.sub.3, 0.4 mmol of lead acetate tetrahydrate Pb(II)(OAC).sub.2.Math.3H.sub.2O and 0.01 to 0.1 mmole manganese(II) acetate tetrahydrate (Mn(II)(OAC).sub.2.Math.4H.sub.2O) along with 30 ml of octadecene and 2 ml of oleic acid were taken in a 100 ml three necked reaction flask. The reaction mixture was purged with flow of N.sub.2 at 100-160 C. for 30 minutes. The temperature of the reaction flask was further increased to 80-200 C. and the reaction was triggered by injecting 2 ml preformed stock solution of oleylammonium chloride. After 1-5 minutes, the heating mantel was removed, and the reaction flask was allowed to cool naturally. Cooled reaction mixture was transferred into a 50 ml centrifuge tube and 10 ml anhydrous ethyl acetate was added to it. The resultant mixture was centrifuged at 10000 rpm for 10 minutes. Finally, the supernatant was discarded, and the precipitated nanocrystals were dispersed and harvested in hexane/toluene/chloroform.

Example 4: Synthesis of Mn Doped CsPbCl.SUB.3-x.Br.SUB.x .Nanocrystals

[0065] Mn doped CsPbCl.sub.3-xBr.sub.x nanocrystals were prepared by following the method stated in Example 3. For obtaining different Cl to Br ratio, the oleylammonium chloride to oleylammonium bromide ratio was adjusted accordingly.

Example 5: Uv-Vis Absorbance Spectra

[0066] FIG. 2 presents UV-Vis absorbance spectra of the Mn-doped nanocrystals. With the increase in bromide content of the nanocrystals, red shifting of the spectra is observed, which indicates lowering of the band gap on bromide alloying.

Example 6: Photoluminescence (PL) Spectra

[0067] FIG. 3 presents PL spectra of the Mn-doped CsPbCl.sub.3-xBr.sub.x nanocrystals. The excitation wavelength was 350 nm. On bromine alloying, the red tuning of the host emission is observed, but the dopant emission position remains fixed. However, drastic reduction in the Mn dopant emission is observed on bromine alloying. This is due to decrease in the efficiency of exciton to dopant energy transfer on reduction of bandgap due to bromine alloying.

Example 7: Photoluminescence Excitation (PLE) Spectra

[0068] The origin of the Mn dopant emission position (600 nm) was selected for investigating the origin of this emission. FIG. 4 presents PLE spectra of Mn-doped CsPbCl.sub.3-xBr.sub.x nanocrystals. The steady red shift in the spectra is well correlated with their corresponding absorbance spectra, which concludes that the emission is originated from the corresponding host nanocrystals.

Example 8: Powder X-Ray Diffraction (XRD) Measurement

[0069] FIG. 5 presents powder XRD patterns of Mn-doped CsPbCl.sub.3-xBr.sub.x nanocrystals. The lowering of 20 degree of the bromine alloying sample clearly demonstrates that the volume of the crystal expanded on bromine alloying and the targeted alloying process is achieved.

Example 9: Yield Calculation

[0070] To calculate the exact yield of the nanocrystals, the reaction was performed using 0.5 mmole of Cs.sub.2CO.sub.3, 1 mmole of Pb(OAc).sub.2.Math.3H.sub.2O, and 0.05 mmole of Mn(OAc).sub.2.Math.4H.sub.2O precursors. After the reaction, the resulting product was purified by centrifugation (20000 rpm, 20 min) using ethyl acetate as non-solvent (Ethyl acetate:reaction mixture=4:1). The purified nanocrystals were dried inside vacuum oven at 80 C. for overnight. The amount of ligand present along with the nanocrystals was calculated by weight loss in the Thermogravimetric analysis (TGA). FIG. 6 discloses the TGA weight loss profile of the nanocrystals. The yield calculation is given in Table 1.

TABLE-US-00001 TABLE 1 Yield Calculation Theoretical Product weight Weight loss Actual Yield Yield with ligand in TGA Yield Percentage 0.446 gm 0.529 gm 18.70% 0.435 97.5

[0071] Therefore, the process shows a yield of 97.5%.