Patent Application
20240067875
The present invention relates to a process for the preparation of B-site doped ABX3 perovskite nanocrystals. More particularly, the present invention provides a process for the preparation of doped ABX3 perovskite nanocrystals, wherein X=Chlorine (Cl), Bromine (Br), and Iodine (I).
Various literature describes the preparation of several doped ABX3 nanocrystals using various methods, which include Hot injection (HI), Ligand Assisted Re-precipitation (LARP), ultrasonication, mechano-chemical, etc. These doped nanocrystals prepared through method other than HI suffer from low photoluminescence quantum yield (PLQY) and poor crystallinity. Kovalenko et al. (Nano Lett. 2015, 15, 3692-3696) invented the HI approach for ABX3 (A=Cs, B═Pb and X═Cl, Br, I) perovskite nanocrystals and this remained the most studied approach for the synthesis of perovskite nanocrystals. This method is termed here as a traditional HI approach. Manganese remained the first dopant to be introduced in this system and Mn doping in CsPbX3 is first reported by Klimov et al. (J. Am. Chem. Soc. 2016, 138, 14954-14961) where they followed this traditional HI approach. The same approach is also followed for doping other dopants by many researchers. The same method is accepted widely for the synthesis of doped nanocrystals. For synthesizing Mn-doped nanocrystals, manganese chloride (MnCl2), lead chloride (PbCl2), and octadecene (ODE) solvent are loaded in a three-neck flask. Then the temperature of the reaction mixture is set at 100-120° C. and purged with argon/nitrogen to remove moisture and oxygen from the system. This is followed by injection of oleic acid (OA), oleylamine (OLA), and trioctylphosphine (TOP) for solubilizing the precursor and stabilizing the formed nanocrystals. The reaction is triggered by injecting a preformed cesium-oleate (Cs-oleate) stock solution at the desired temperature. Finally, the reaction is quenched by dipping the flask in an ice bath. This traditional HI approach has the following disadvantages:
However, several modifications have been done in the art to improve the doping process.
CN108753286 reported Mn doped CsPbCl3 perovskite nanocrystals prepared by microwave-assisted thermal injection method. CN108865126 modified the traditional HI approach and obtained Mn doped CsPbCl3 and CsPbCl3-xBrx nanocrystals. This was done by taking different stock solutions. One sock solution contains PbCl2 and MnCl2 (Pb:Mn=1:2) along with OA, OLA and TOP; and other stock solution contains Cs-oleate; mixing them at 190° C. results in Mn doped CsPbCl3 nanocrystals. For Mn doping in CsPbCl3-xBrx nanocrystals, the process remains same. Instead of only PbCl2, separate PbBr2 and PbCl2 precursor solutions were prepared. Different amounts of PbCl2 and PbBr2 stock solutions were mixed and Cs-oleate was added to this mixed stock solution at 190° C. for triggering the reaction. By varying the stock solution amount, the chloride to bromide ratio in the doped nanocrystals was adjusted. The reaction was quenched by ice cooling. The process involved Mn and Pb precursor loss as well as use of phosphine, which put a bar on their commercial feasibility.
CN108929685A relates to a preparation method of Mn-doped CsPbCl3 perovskite quantum dot comprising the steps of putting the Cs2CO3 with octadecene and oleic acid in the three-necked bottle, heating to 95-105 degrees centigrade; raising the temperature to 135-145 degrees centigrade; then heating to 175-185 degrees centigrade, rapidly injecting oleic acid cesium precursor, reacting for 2-4 min, and cooling in a fast-cooling bath. CN110218561A relates to a method of improving manganese doping CsPbCl3, wherein the method comprises preparing a cesium precursor solution; combining octadecene, oleic acid, oleylamine, trioctyl phosphine, lead chloride, manganese chloride and nickel chloride Mixing; forming Ni and Mn double doped CsPbCl3 nanocrystals; Obtaining Ni and Mn double doped CsPbCl3 nanocrystalline solution.
WO2017100950A1 relates to methods of forming quantum dots of the formula CsPbX3, wherein X is a halogen (CI, Br, or I). It comprises lead precursors such as lead (II) oleate and lead (II) stearate, cesium precursors such as cesium oleate and cesium stearate, and halide precursors such as benzyl halide. The molar ratio of cesium:lead (II) is from about 10:1 to about 1:10. Lijia Liu et al. discloses preparation of Mn-doped CsPb(Br/Cl)3 nanocrystals with Cs2CO3 and PbAc2 as non-halide precursors in 1:1 ratio and doping of Mn is done using MnCl2. The synthesis is performed at room temperature and hence ice-cooling/quenching step is not required. It also does not involve use of phosphine.
David Parobek et al. relates to the synthesis of Mn-doped CsPbBr3 nanocrystals via the formation of an intermediate structure (L2[Pb1-xMnx]Br4, L=ligand) before the hot-injection of the Cs precursor, which contains the same Mn—Br coordination present in Mn-doped CsPbBr3 nanocrystals. A strong correlation was observed between the Mn luminescence intensities of L2[Pb1-xMnx]Br4 and Mn-doped CsPbBr3 nanocrystals, suggesting the possible role of L2[Pb1-xMnx]Br4 as the structural precursor to Mn-doped CsPbBr3 nanocrystals. Ping Yang et al. relates to Mn:CsPb(Cl/Br)3 nanocrystals (NCs) with different halogen ratios obtained by one-pot hot injection synthesis and halogen ion exchange. Xinmei Hou et al. relates to an improved hot injection technique, namely microwave-assisted hot injection, for mass production of Mn2+-doped CsPbCl3 (Mn2+:CsPbCl3) perovskite nanocrystals (NCs). Yiwen Zhang et al. discloses a simplified solid-state mechanochemical approach to synthesize Mn-doped CsPbCl3 nanocrystals and investigates the structure and luminescence properties of the as-synthesized nanocrystals. Xiaoshang Tang et al. discloses Mn-doped CsPbX3 (X═Br, Cl) quantum dots (QDs) were synthesized at room temperature via a facile strategy by introducing dimethyl sulfoxide (DMSO)—MnBr2/PbX2 composite as a precursor.
Narayan Pradhan et al. discloses facts related to selecting the precursors and their ratios, the reaction temperature, and some tricks for obtaining high-quality CsPbX3 nanocrystals. For deaerating the mixture, purging with argon or nitrogen is required at a minimum temperature (typically 100-120° C.). The ratio of Pb to Cs ideally might be chosen as 1:1, and in this case, alkylammonium halides might be used for supplying adequate halide ions. These reactions can be performed by injecting Cs(I) precursor or halide precursor at high temperature for nucleating respective perovskite nanocrystals, keeping all other reagents in the reaction flask. Andries Meijerink et al. discloses preparation of Mn-doped CsPbCl3 perovskite nanocrystals with CsAc and PbAc2 as non-halide precursors used in equimolar amount and doping of Mn is done using MnAc2 at an amount of 5%. The synthesis is performed at room temperature and hence ice-cooling/quenching step is not required. It also does not involve use of phosphine. Oleic acid (OA) and oleylamine (OLAM) were chosen as ligands and reaction is performed under N2 atmosphere. The yield obtained is 70%. Although the above-mentioned methods have been used to overcome some of the inherent drawbacks, most of the challenges are still existing. In compared to all the methods, the inventors report a novel, synthetic process to overcome the above-mentioned issues related to traditional HI approach. Some of the advantages of the process of the present invention over all other reported HI approach include no use of phosphine, no reprecipitation of lead precursor, 100% yield (with respect to Pb/Cs precursor), no ice quenching requirement, and Mn-doping with minimal amount of Mn precursor loading (5-50% with respect to Pb/Cs precursor) for intense Mn d-d emission.
Further, traditional synthesis process for Mn-doped CsPbX3 perovskite nanocrystals is associated with the following problems:
All these issues create problem in their large-scale production of perovskite nanocrystals. The process of the present invention overcomes the aforementioned drawbacks.
The present invention describes a process the preparation of B-site doped ABX3 perovskite nanocrystals, wherein the process comprises: a) loading non-halide precursors of A, B, and dopant in three neck flasks along with long chain acid and olefin; b) purging of the reaction mixture under heating; and c) finally injecting alkylammonium chloride stock solution in the reaction mixture at a desired temperature.
The advantages of the synthesis over the cited prior arts are as follows:
The primary objective of the present invention is to provide a process for preparation of D-doped ABX3 perovskite nanocrystals or B-site doped ABX3 perovskite nanocrystals, the process comprising:
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.
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.
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.
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”.
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.
The term “including” is used to mean “including but not limited to”. “Including” and “including but not limited to” are used interchangeably.
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.
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.
The present invention discloses a process for preparation of D-doped ABX3 perovskite nanocrystals or B-site doped ABX3 perovskite nanocrystals. The process comprises:
In another embodiment, the process further comprises preparation of D-doped AB11-yB2yX3 perovskite nanocrystals, wherein B1 comprises silver (Ag), copper (Cu), indium (In), gold (Au), thalium (Tl), sodium (Na) and potassium (K); B2 comprises indium (In), bismuth (Bi) and antimony (Sb); and y=0 to 1.
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).
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.
In another embodiment, the non-halide precursor source is selected from carbonate, acetate, nitrate, acetylacetonate, oleate, undecylenate, myristate, laurate, or palmitate.
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.
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.
In yet another embodiment, the process includes no use of phosphine and no re-precipitation of lead precursor.
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.
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.
In another embodiment, the invention can be extended to other doped perovskite materials such as D-doped ABCl3-xBrx (D=Mn, A=Cs, B═Pb, and x=1 to 3).
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.
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.
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.
In a typical synthesis 0.2 mmol of Cs2CO3, 0.4 mmol of lead acetate tetrahydrate Pb(II)(OAC)2·3H2O and 0.01 to 0.1 mmole manganese(II) acetate tetrahydrate (Mn(II)(OAC)2·4H2O) 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 N2 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.
Mn doped CsPbCl3-xBrx 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.
The origin of the Mn dopant emission position (600 nm) was selected for investigating the origin of this emission.
To calculate the exact yield of the nanocrystals, the reaction was performed using 0.5 mmole of Cs2CO3, 1 mmole of Pb(OAc)2·3H2O, and 0.05 mmole of Mn(OAc)2·4H2O 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).
Therefore, the process shows a yield of 97.5%.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202221048238 | Aug 2022 | IN | national |
