A method for synthesis of metal halide perovskite (cspbbr3) nano / microcrystals

Abstract

The present invention relates to metal halide perovskite (CsPbBr3) nano / microcrystals. Specifically, the present invention relates to a method for the synthesis of metal halide perovskite (CsPbBr3) nano / microcrystals. The present invention uses an easy, scalable low temperature growth of metal halide nanoparticles like CsPbBr3. The method uses a clever play on the solubility and ion exchange mechanism to precipitate nano and microcrystals of metal halide perovskites. The synthesis resulted in stable perovskite crystals with high photo- luminescence, ultralow dark current and control over their morphology. The combination of ultralow dark current, high responsivity, exceptional detectivity, and broad-band photon detection capabilities makes these crystals an excellent choice for upcoming sensors and detector technologies.

Description

A METHOD FOR SYNTHESIS OF METAL HALIDE PEROVSKITE (CsPbBr3) NANO / MICROCRYSTALSFIELD OF THE INVENTION

[0001] The present invention relates to metal halide perovskite (CsPbBr3) nano / microcrystals. Specifically, the present invention relates to a method for the synthesis of metal halide perovskite (CsPbBrfi nano / microcrystals. The synthesis resulted in stable perovskite crystals with high photo-luminescence, ultralow dark current and control over their morphology. The combination of ultralow dark current, high responsivity, exceptional detectivity, and broad-band photon detection capabilities makes these crystals an excellent choice for upcoming sensors and detector technologies.BACKGROUND OF THE INVENTION

[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

[0003] Metal halide perovskites such as CsPbBr3have interesting optoelectronic properties. They are potential candidates for broad spectrum photon detectors. They are very efficient in detecting visible light from 540 nm to x-rays and gamma rays. They are a direct band gap material and have immense potential in optoelectronic application. They are also used for certain catalytic reactions. The photodetectors or optoelectronic applications would be improved drastically if we can reduce the dark current and controlling morphology could have interesting catalytic effects.

[0004] An article entitled “Improving the Stability of CsPbBr3Perovskite Nanocrystals by Peroxides Post-treatment” by L. Min et al. and published in the journal “Front. Mater., Sec. Energy Materials, Volume 6 - 2019” reports the synthesis of CsPbBr3perovskite nanocrystals (NCs) using cesium-oleate, lead bromide, 1 -octadecene (ODE), oleic acid (OA) and oleyl amine (OAm) at 180 DC which are further oxidized by benzoyl peroxide (BPO) to generate a PbO layer on the surface of the nanocrystals to provide strong photostability to the crystals (phase JCPDS 25-0211), useful for optoelectronic applications.

[0005] An article entitled “Shape-controlled Synthesis of All-inorganic CsPbBr3 Perovskite Nanocrystals with Bright Blue Emission” by L. Zhiqin et al. and published in the journal “ACS Appl. Mater. Interfaces 2016, 8, 42, 28824-28830” reports the shape-controlledsynthesis of CsPbBr3perovskite nanocrystals (NCs) using cesium-oleate, lead bromide, octadecene (ODE), oleic acid (OA) and oleyl amine (OAm) at 90 DC wherein a change in the ratio of the oleic acid and oleyl amine affords nanocrystals with different morphologies such as single and lamellar-structured 0D quantum dots, face-to-face stacking 2D nanoplatelets and flat lying 2D nanosheets. The 2D nanoplatelets and nanosheets display the XRD pattern of orthorhombic CsPbBr3.

[0006] An article entitled “Ethanol-water-assisted room temperature synthesis of CsPbBr3 / SiO2 nanocomposites with high stability in ethanol” by L. Wen et al. and published in the journal “J Mater Sci 54, 3786-3794 (2019)” reports the room temperature synthesis of CsPbBr3nanoparticles by conducting the reaction between CsBr and PbBr2in the presence of oleyl amine (OAm) and oleic acid (OA) in DMF, followed by the addition of ethanol-water (14.8:2) and centrifugation to afford CsPbBr3nanoparticles as a precipitate.

[0007] CN112964687A discloses the preparation of fluorescent perovskite nanomaterials CsPbBr3and CsPbBri5Ii5@MSNs using CsBr, PbBr2, DMF, toluene, oleic acid (OA) and oleylamine (OLA) at room temperature for CsPbBr3, and CsBr, Pbl2, mesoporous silica (MSNs) and DMSO at 155 °C for CsPbBn5Ii5@MSNs.

[0008] An article entitled “CsPbX3Quantum Dots for Lighting and Displays: RoomTemperature Synthesis, Photoluminescence Superiorities, Underlying Origins and White Light-Emitting Diodes” by L. Xiaoming et al. and published in the journal “Adv. Funct. Mater. 2016, 26, 2435-2445” reports the preparation of inorganic perovskite quantum dots (IPQDs), CsPbBr3using CsBr, PbBr2, DMF, toluene, oleic acid (OA) and oleylamine (OLA) at room temperature via supersaturated recrystallization (SR) technique. Similarly other IPQDs were synthesized using corresponding PbX2and CsX (X = Cl, Br, I) precursors.

[0009] The current technology uses various solution-based techniques such as hot injection, ion-exchange, solvent crystallization etc., Chemical vapor deposition (CVD), and coevaporation. These techniques are good for producing microcrystals but most solution techniques have problems regarding the size of the crystal and high dark current, whereas vapor deposition techniques use very high temperatures and also face challenges with high dark current.

[0010] Therefore, there is an unmet need in the art to develop easy, scalable low temperature growth of metal halide perovskites with high photo-luminescence and very low leakage current that overcomes one or more drawbacks of the prior arts.OBJECTIVE OF THE INVENTION

[0011] An objective of the present invention is to provide metal halide perovskite (CsPbBr3) nano / microcry stals .

[0012] Another objective of the present invention is to provide a method for the synthesis of metal halide perovskite (CsPbBr3) nano / microcrystals.

[0013] Another objective of the present invention is to provide stable perovskite crystals with high photo-luminescence, ultralow dark current and control over their morphology.SUMMARY OF THE INVENTION

[0014] The present invention relates to metal halide perovskite (CsPbBr3) nano / microcrystals. Specifically, the present invention relates to a method for the synthesis of metal halide perovskite (CsPbBr3) nano / microcrystals. The synthesis resulted in stable perovskite crystals with high photo-luminescence, ultralow dark current and control over their morphology.

[0015] In an aspect, the present invention provides a method for synthesis of metal halide perovskite (CsPbBr3) nano / microcrystals comprising the steps of: a) mixing peroxide with alcohol in a vial, to form a solution; b) adding a first and a second precursor for the synthesis of crystals in the solution; c) adding a surfactant into the solution for the growth of crystals; d) placing substrate at the bottom of the vial containing the solution, to collect the precipitated crystals; e) heating the solution to a temperature in the range of 30 to 60 °C; and f) removing and rinsing the substrate after 3 to 4 hrs, followed by blow drying to obtain metal halide perovskite nano / microcrystals.

[0016] In another aspect of the present invention, the peroxide is hydrogen peroxide (H2O2).

[0017] In another aspect of the present invention, the peroxide is present in the range of 0.02 to 2 wt. % of total wt. % of alcohol.

[0018] In another aspect of the present invention, the alcohol is selected from a group consisting of methanol, ethanol and isopropyl alcohol (IP A).

[0019] In another aspect of the present invention, the first precursor for the synthesis of metal halide perovskite (CsPbBr3) nano / microcrystals is cesium bromide (CsBr).

[0020] In another aspect of the present invention, the first precursor is present in a concentration in the range of 0.5 - 50 Hg / ml of the solution.

[0021] In another aspect of the present invention, the second precursor for the synthesis of metal halide perovskite (CsPbBr3) nano / microcrystals is an iodide, wherein the iodide is selected from a group consisting of CsI, PbL. and GcL

[0022] In another aspect of the present invention, the second precursor for the synthesis of metal halide perovskite (CsPbBr3) nanocrystals is lead iodide ( Pbl2)

[0023] In another aspect of the present invention, the second precursor is present in a concentration in the range of 0.2 - 10 pg / ml of the solution.

[0024] In another aspect of the present invention, the surfactant is selected from a group consisting of inorganic acids, amines, amides and organic acid.

[0025] In another aspect of the present invention, the surfactant selected is organic acid.

[0026] In another aspect of the present invention, the organic acid is selected from a group consisting of octanoic acid, oleic acid, hexanoic acid, and acetic acid.

[0027] In another aspect of the present invention, the surfactant is present in a concentration in the range of 0. 1 - 50 pl / ml of the solution.

[0028] In another aspect of the present invention, the synthesized metal halide perovskite (CsPbBr3) nano / microcrystals have ultra-low dark current and control over their morphology.

[0029] Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments.BRIEF DESCRIPTION OF FIGURES

[0030] Figure 1 illustrates schematically the process of synthesizing CsPbBr3crystals of very low leakage current.

[0031] Figure 2 illustrates the images of bottles with 15 ml ethanol, PbL. and CsBr (a) contains 75 pl Octanoic acid, (b) contains 5 pl 3% H2O2, (c) contains 30 pl 3% H2O2 and (d) contains a mix of 75 pl Octanoic acid and 30 pl 3% H2O2.

[0032] Figure 3 illustrates the XRD of the as-synthesized crystal.

[0033] Figure 4 illustrates the optical and PL images of CsPbBr3microcrystals grown.

[0034] Figure 5 illustrates the PL spectrum of the sample.

[0035] Figure 6 illustrates the ED AX spectrum and the elemental mapping.

[0036] Figure 7 illustrates the FESEM images of CsPbBr3crystals grown by changing the organic acids and alcohols and their combinations.

[0037] Figure 8 illustrates (a) the optical image of a CsPbBr3device, (b) the dark current at room temperature and (c) the photocurrent of the device at room temperature.

[0038] Figure 9 illustrates the current voltage (I-V) characteristic of the device when irradiated with 2.5 mR / hr X-ray and the I-V characteristic without irradiation.

[0039] Figure 10 illustrates (a) image of the CsPbBr3device under test (b) The currentvoltage (I-V) plot is presented for the CsPbBr3device under test in a dark condition, measured using Keysight electrometer B2985A. (c) The current-voltage (I-V) plot is presented for the CsPbBr3device under test under external illumination.

[0040] Figure 11 illustrates (a), (b), and (c) are the photocurrent, responsivity and detectivity of the device as measured across an extensive wavelength range spanning from 350 nm to 700 nm.DETAILED DESCRIPTION OF THE INVENTION

[0041] The following is a full description of the disclosure's embodiments. The embodiments are described in such a way that the disclosure is clearly communicated. The level of detail provided, on the other hand, is not meant to limit the expected variations of embodiments; rather, it is designed to include all modifications, equivalents, and alternatives that come within the spirit and scope of the current disclosure as defined by the attached claims. Unless the context indicates otherwise, the term "comprise" and variants such as "comprises" and "comprising" throughout the specification are to be read in an open, inclusive meaning, that is, as "including, but not limited to."

[0042] When "one embodiment" or "an embodiment" is used in this specification, it signifies that a particular feature, structure, or characteristic described in conjunction with the embodiment is present in at least one embodiment. As a result, the expressions "in one embodiment" and "in an embodiment" that appear throughout this specification do not necessarily refer to the same embodiment. Furthermore, in one or more embodiments, the specific features, structures, or qualities may be combined in any way that is appropriate.

[0043] Unless the content clearly demands otherwise, the singular terms "a," "an," and "the" include plural referents in this specification and the appended claims. Unless the content explicitly mandates differently, the term "or" is normally used in its broad definition, which includes "and / or."

[0044] In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, reaction conditions, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description are approximations that can vary depending upon the desiredproperties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be constructed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable.

[0045] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein.

[0046] All processes described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

[0047] The headings and abstract of the invention provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.

[0048] The following discussion provides many example embodiments of the inventive subject matter. Although each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed.

[0049] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.

[0050] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements foundherein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and / or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description that follows, and the embodiments described herein, is provided by way of illustration of an example, or examples, of particular embodiments of the principles and aspects of the present disclosure. These examples are provided for the purposes of explanation, and not of limitation, of those principles and of the disclosure.

[0051] It should also be appreciated that the present invention can be implemented in numerous ways, including as a system, a method or a device. In this specification, these implementations, or any other form that the invention may take, may be referred to as processes. In general, the order of the steps of the disclosed processes may be altered within the scope of the invention.

[0052] Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.

[0053] In a general embodiment, the present invention relates to metal halide perovskite (CsPbBrft nano / microcrystals. Specifically, the present invention relates to a method for the synthesis of metal halide perovskite (CsPbBrft nano / microcrystals. The synthesis resulted in stable perovskite crystals with high photo-luminescence, ultralow dark current and control over their morphology.

[0054] In an embodiment, the present invention provides a method for synthesis of metal halide perovskite (CsPbBr3) nano / microcrystals comprising the steps of: a) mixing peroxide with alcohol in a vial, to form a solution; b) adding a first and a second precursor for the synthesis of crystals in the solution; c) adding a surfactant into the solution for the growth of crystals; d) placing substrate at the bottom of the vial containing the solution, to collect the precipitated crystals; e) heating the solution to a temperature in the range of 30 to 60 °C; and f) removing and rinsing the substrate after 3 to 4 hrs, followed by blow drying to obtain metal halide perovskite nano / microcrystals.

[0055] In another embodiment of the present invention, the peroxide is hydrogen peroxide (H2O2). Though, the peroxide used is not limited to H2O2. Further, the peroxide is present in the range of 0.02 to 2 wt.% of total wt.% of alcohol. Preferably, the peroxide is present 0.2 wt.% of total wt.% of alcohol.

[0056] In another embodiment of the present invention, the alcohol is selected from a group consisting of methanol, ethanol and isopropyl alcohol (IP A).

[0057] In another embodiment of the present invention, the first precursor for the synthesis of metal halide perovskite (CsPbBr3) nano / microcrystals is cesium bromide (CsBr). Further, the first precursor is present in a concentration in the range of 0.5 - 50 g / ml of the solution. Preferably, the first precursor is present in a concentration in the range of 3 - 6 g / ml of the solution.

[0058] In another embodiment of the present invention, the second precursor for the synthesis of metal halide perovskite (CsPbBr3) nano / microcrystals is an iodide, wherein the iodide is selected from a group consisting of CsI, Pbl2. and Gcl2Further, the second precursor for the synthesis of metal halide perovskite (CsPbBr3) nanocrystals is lead iodide (Pbl2) Also, the second precursor is present in a concentration in the range of 0.2 - 10 pg / ml of the solution. Preferably, the second precursor is present in a concentration in the range of 1 - 4 pg / ml of the solution.

[0059] In another embodiment of the present invention, the use of a peroxide in the presence of an alcohol increases the solubility of the metal iodide precursors, during the synthesis of the metal halide perovskite (CsPbBr2) nano / microcrystals. Thus, the addition of H2O2 helps in increasing the solubility of iodides such as CsI, Pbl2. GeB, etc.

[0060] In another embodiment of the present invention, the addition of small quantities of peroxides to alcohols like methanol, ethanol or IPA increases the solubility of Pbl2in them. As shown in Figure 2 the color sample d exhibited maximum solubility of Pbl2. This causes CsPbBr3to nucleate and grow in the solution.

[0061] In another embodiment of the present invention, the surfactant is selected from a group consisting of inorganic acids, amines, amides and organic acid. Preferably, the surfactant selected is organic acid. More preferably, the organic acid is selected from a group consisting of octanoic acid, oleic acid, hexanoic acid, and acetic acid. Though, the acid or ligand used is not limited to organic acids. Adding organic acids improves the solubility as well as help in controlling the morphology of the crystals.

[0062] In another embodiment of the present invention, the surfactant is present in a concentration in the range of 0.1 - 50 pl / ml of the solution. Preferably, the surfactant is present in a concentration of 5 pl / ml of the solution.

[0063] In another embodiment of the present invention, the use of inorganic acid like HBr will result in poor growth and the nature of the organic acid used in the present invention could affect the morphology of the crystal.

[0064] In another embodiment, the solution of the present invention is heated to a temperature in the range of 30 to 60 °C. Preferably, the solution of the present invention is heated to a temperature in the range of 40 to 50 °C. Most preferably, the solution of the present invention is heated to a temperature of 45°C.

[0065] In another embodiment of the present invention, as shown in Figure 6, the EDAX spectrum and the elemental mapping done on the sample shows that the composition is that of CsPbBr3. The Br is present in the range of 45 to 50 wt.%, the Cs is present in the range of 20 to 25 wt.% and the Pb is present in the range of 30 to 35 wt.% of the total composition of metal halide perovskite (CsPbBr3) nano / microcrystals.

[0066] In yet another embodiment, the present invention provides an easy, scalable low temperature growth of metal halide nanoparticles like CsPbBr3. The novel technique of the present invention uses very low temperatures, and uses a chemical reaction with a relatively large window of growth. The shape and size of the crystal can be controlled using the concentration and surfactants used. The method uses a clever play on the solubility and ion exchange mechanism to precipitate nano and microcrystals of metal halide perovskites. Though many ion exchange mechanisms are known, changing the solubility of Pbl2or other iodides is unique to the method of the present invention. The synthesis resulted in stable perovskite crystals with high photo-luminescence and very low leakage current.

[0067] In another embodiment, the present invention relates to a low-temperature synthesis of metal halide perovskite (CsPbBr3) nano / microcrystals with ultralow dark current and control over their crystal morphology. The novel growth method of the present invention uses peroxides to increase the solubility of iodides and use this discovery to grow CsPbBr3crystals of very low leakage current with great control over their crystal morphology. Thus, the as- synthesized microcrystals have very low leakage current making it attractive for detector applications. The method of the present invention is unique and produces high-quality microcrystals that exhibits excellent optoelectronic properties and could be useful as photodetectors or LEDs.

[0068] While the foregoing describes various embodiments of the disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enablea person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.EXAMPLES

[0069] The present invention is further explained in the form of the following examples. However, it is to be understood that the following examples are merely illustrative and are not to be taken as limitations upon the scope of the invention.

[0070] Example 1: General process for the synthesis of metal halide perovskite (CsPbBr3) nano / microcrystals.The solution growth was carried out in a glass vial of 2 cm diameter. First added alcohol (15 ml) such as ethanol mixed with 0.2% of H2C>2 in the glass vial. The addition of H2C>2 helps in increasing the solubility of iodides such as CsI, Pbl2. GcE. etc. Then added 40 mg of CsBr to the solution. Then added Pbl2(10 mg), followed by 75 p.1 of an organic acid such as Octanoic acid, Oleic acid, hexanoic acid, or acetic acid. The use of inorganic acid like HBr will result in poor growth and the nature of the organic acid could affect the morphology of the crystal. The substrate on which the precipitated crystal is collected is then gently placed at the bottom of the vial with the desired surface facing up. A hotplate is then heated between 50 - 70°C and the vial is kept on top of it which raises the temperature of the liquid to 40-50°C. The color of the solution changes to yellowish within a few minutes and then to orangish after an hour as shown in Figure 1. The substrate is removed from the solution after 3-4 hrs and is dipped in Isopropyl alcohol followed by blow drying.Example 2: Morphological and optical features of the synthesized metal halide perovskite (CsPbBr3) nano / microcrystals.Figure 3 shows the XRD of the as-synthesized crystal. From XRD it is clear that the crystals are in the orthorhombic phase.Figure 4 shows the optical and PL images of CsPbBr3microcrystals grown.Figure 5 shows the PL spectrum of the sample showing a very narrow PL emission centered at 540 nm and a FWHM of 98 meV.Figure 7 shows the FESEM images of CsPbBr3crystals grown by changing the organic acids and alcohols and their combinations.Figure 8 shows (a) is the optical image of a CsPbBr3device, (b) is the dark current at room temperature and (c) is the photocurrent of the device at room temperature.Figure 9 shows the I-V characteristic of the device when irradiated with 2.5 mR / hr X-ray and the IV characteristic without irradiation.Example 3: Dark current and optical responses of the CsPbBr3deviceThe use of CsPbBr3for photon detection was further verified by making active devices out of them using an already-reported method. ITO was used as the electrode material. The I-V scan of the device was measured using Keysight electrometer B2985A. The dark current was 2.6 fA at IV bias under dark conditions and rose to 3.8 nA when illuminated with 470 nm LED of 10 mW / cm2intensity as shown in Figure 10. The current rose by more than one order of magnitude.The on-off current ratio (Ion / Ioff) and the responsivity (R) of the device were calculated using the relations,Ion > hight and!off i darkwherein, 1^ is the current under illumination and Ida* is the dark current, P is the intensity of the incident light on the device, and A is the area of the device. The Dark current measured using the electrometer gives a current on / off ratio of 106, and a responsivity above 3.5 AAV at 1 V bias in the wavelength range between 350 nm - 520 nm.The detectivity is given bywherein e is the charge of an electron. The device's low dark current, in conjunction with its impressive photocurrent generation, results in a detectivity that is remarkably high. For a broad range of spectra (ranging from 350 nm to 530 nm), this detectivity is on the order of 1015Jones at IV bias. Notably, the device exhibits discernible photoresponse beginning at wavelengths lower than 550 nm.

[0071] A skilled artisan will appreciate that the quantity and type of each ingredient can be used in different combinations or singly. All such variations and combinations would be falling within the scope of present disclosure.

[0072] The foregoing examples are merely illustrative and are not to be taken as limitations upon the scope of the invention. Various changes and modifications to the disclosed embodiments will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the scope of the invention.ADVANTAGES OF THE PRESENT INVENTION

[0073] The present invention is to provide a method for the synthesis of metal halide perovskite (CsPbBr3) nano / microcrystals.

[0074] The present invention is to provide a method that uses peroxide in the presence of an alcohol to increase the solubility of the metal halide precursors, during the synthesis of the metal halide perovskite (CsPbBr3) nano / microcrystals,

[0075] The present invention is to provide an easy, scalable low-temperature growth of metal halide nanoparticles like CsPbBr3.

[0076] The present invention is to provide stable perovskite crystals with high photo- luminescence, ultralow dark current and control over their morphology.

[0077] The present invention is to provide microcrystals that have very low leakage current making it attractive for detector applications and could be useful as photodetectors or LEDs.

Claims

We Claim:

1. A method for synthesis of metal halide perovskite (CsPbBr3) nano / microcrystals comprising the steps of: a) mixing peroxide with alcohol in a vial, to form a solution; b) adding a first and a second precursor for the synthesis of crystals in the solution; c) adding a surfactant into the solution for the growth of crystals; d) placing substrate at the bottom of the vial containing the solution, to collect the precipitated crystals; e) heating the solution to a temperature in the range of 30 to 60 °C; and f) removing and rinsing the substrate after 3 to 4 hrs, followed by blow drying to obtain metal halide perovskite nano / microcrystals.

2. The method as claimed in claim 1, wherein the peroxide is hydrogen peroxide (H2O2).

3. The method as claimed in claim 1, wherein the peroxide is present in the range of 0.02 to 2 wt.% of total wt.% of alcohol.

4. The method as claimed in claim 1, wherein the alcohol is selected from a group consisting of methanol, ethanol and isopropyl alcohol (IPA).

5. The method as claimed in claim 1, wherein the first precursor for the synthesis of metal halide perovskite (CsPbBr3) nano / microcrystals is cesium bromide (CsBr).

6. The method as claimed in claim 1, wherein the first precursor is present in a concentration in the range of 0.5 - 50 |ig / ml of the solution.

7. The method as claimed in claim 1, wherein the second precursor for the synthesis of metal halide perovskite (CsPbBr3) nano / microcrystals is an iodide and the iodide is selected from a group consisting of CsI, Pbl2. and Gcl28. The method as claimed in claim 7, wherein the second precursor for the synthesis of metal halide perovskite (CsPbBr3) nanocrystals is lead iodide (Pbl2).

9. The method as claimed in claim 1, wherein the second precursor is present in a concentration in the range of 0.2 - 10 |ig / ml of the solution.

10. The method as claimed in claim 1, wherein the surfactant is selected from a group consisting of inorganic acids, amines, amides and organic acid.

11. The method as claimed in claim 10, wherein the surfactant selected is organic acid.

12. The method as claimed in claim 10, wherein the organic acid is selected from a group consisting of octanoic acid, oleic acid, hexanoic acid, and acetic acid.

13. The method as claimed in claim 1, wherein the surfactant is present in a concentration in the range of 0.1 - 50 pl / ml of the solution.

14. The method as claimed in claim 1, wherein the synthesized metal halide perovskite (CsPbBr3) nano / microcrystals have ultra-low dark current and control over their morphology.