TWO DIMENSIONAL ORGANO-METAL HALIDE PEROVSKITE NANORODS

Abstract

Organometal halide perovskites are provided as nanoparticles for the construction of efficient light harvesters in photovoltaic solar cells. Further provided are methods of manufacturing the nanoparticles and uses thereof.

Claims

1.-50. (canceled)

51. A perovskite nanoparticle selected from a nanorod and a nanocube, the nanoparticle having a length of between 3 and 200 nm.

52. A perovskite nanoparticle selected from a nanorod and a nanocube, the nanoparticle having an aspect ratio of between 1 and 100.

53. The nanoparticle according to claim 51, having an aspect ratio of between 1 and 100.

54. The nanoparticle according to claim 51, wherein the nanorod is of a perovskite material comprising at least one organic-inorganic perovskite.

55. The nanoparticle according to claim 51, wherein the perovskite is or comprises a lead halide.

56. A perovskite nanoparticle selected from a nanorod and a nanocube, the nanoparticle having an aspect ratio of between 1 and 100, the nanoparticle being of a perovskite material comprising lead halide.

57. The nanoparticle according to claim 56, wherein the organic-inorganic perovskite is of the formula R.sub.2(A).sub.n−1M.sub.nX.sub.3n+1 (1<n), wherein R is an organic cation, A is an organic cation, M is a metal and X is a halogen.

58. A process for preparing perovskite nanoparticles, the nanoparticles being selected from perovskite nanorods and nanocubes, the process comprising treating a solution comprising precursors of at least one perovskite material under conditions allowing growth of the perovskite nanoparticles.

59. The process according to claim 58, further comprising obtaining one or more organic cation precursors solution, optionally containing an anion precursor of the perovskite material.

60. The process according to claim 59, further comprising two or more organic cation precursors solutions, wherein one or more organic cation precursor comprises a long carbon chain, while another organic cation comprises a short carbon chain.

61. The process according to claim 60, further comprising obtaining one or more anion precursors solution containing an anion precursor of the perovskite material.

62. The process according to claim 61, further comprising obtaining one or more ligand precursors solution, optionally containing an anion precursor of the perovskite material.

63. The process according to claim 62, further comprising contacting the metal precursors solution with the organic cation precursors solution and optionally with the anion precursors solution of the perovskite material to afford a mixture.

64. The process according to claim 63, wherein the metal precursor solution comprises at least one lead halide.

65. The process according to claim 64, wherein the lead halide is PBI.sub.2 and/or PbBr.sub.2.

66. The process according to claim 63, wherein the metal precursor solution comprises at least one organic solvent.

67. The process according to claim 66, wherein the organic cation precursor solution comprises at least one organic cation precursor selected from octylamine iodide, octylamine bromide, methylamine iodide, methylamine bromide, decylamine iodide, decylamine bromide, octadecylamine iodide and octadecylamine bromide.

68. The process according to claim 58, wherein the conditions allowing growth of the perovskite nanoparticles comprise mixing the solution at room temperature or at a temperature below 200° C., below 100° C., below 90° C. or below 80° C.

69. The process according to claim 58, comprising: 1) obtaining a solution of at least one lead halide; 2) obtaining a solution of at least one amine selected from methylamine iodide or methylamine bromide; and 3) mixing solutions (1) and (2) under conditions permitting formation of the nanoparticles.

70. The process according to claim 69, comprising: 1) obtaining a solution of PbI.sub.2 or PbBr.sub.2 in a solvent; 2) obtaining a solution of methylamine iodide or methylamine bromide in a solvent; 3) obtaining a solution of octylammonium iodide (OAI), oleic acid (OAc) and octadecene; 4) mixing solutions (1), (2) and (3) under conditions permitting formation of the nanoparticles.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0313] In order to better understand the subject matter that is disclosed herein and to exemplify how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

[0314] FIG. 1 provides TEM images and inset FFTs of the nanorods made from various halide compositions according to the invention.

[0315] FIGS. 2A-D are HRTEM images of the nanorods shown in FIG. 1.

[0316] FIGS. 3A-B provide: FIG. 3A—XRD of the various nanorods compositions. The wide peaks support the TEM observation of accepting nano-sized particles. FIG. 3B provides an electron diffraction image of (CH.sub.17NH.sub.3).sub.2(CH.sub.3NH.sub.3).sub.2Ph.sub.3I.sub.10 nanorods.

[0317] FIGS. 4A-D provide: FIG. 4A an image of the emitting nanorods dispersions composed of various halide mixtures. FIG. 4B provides absorbance spectra of the 2D perovskite nanorods of various halides compositions. FIG. 4C provides PL spectra of the 2D perovskite nanorods; and FIG. 4D provides PL-QY and band gap energies measured and calculated by Tauc plot of the perovskite nanorods compositions.

[0318] FIGS. 5A-D provide Tauc plots of the various OMHP-nanorod compositions: FIG. 5A—(C.sub.8H.sub.17NH.sub.3).sub.2(CH.sub.3NH.sub.3).sub.2Pb.sub.3I.sub.10, FIG. 5B—(C.sub.8H.sub.7NH.sub.3).sub.2(CH.sub.3NH.sub.3).sub.2Pb.sub.3(I.sub.xBr.sub.1-x).sub.10, (I>Br), FIG. 5C—(C.sub.8H.sub.7NH.sub.3).sub.2(CH.sub.3NH.sub.3).sub.2Pb.sub.3(I.sub.xBr.sub.1-x).sub.10, (I<Br), and FIG. 5D—(C.sub.8H.sub.17NH.sub.3).sub.2(CH.sub.3NH.sub.3).sub.2Pb.sub.3Br.sub.10.

[0319] FIGS. 6A-F provide TEM images of MAPbI.sub.3 QDs/NRs prepared at various OAI/OAc ratios: FIG. 6A—100% OAc; FIG. 6B—OAI/OAc=0.075. FIG. 6C—OAI/OAc=0.186. FIG. 6D—OAI/OAc=0.250; the two figures are taken from the same sample in different areas; FIG. 6E—100% OAI. FIG. 6F—schematic illustration of the suggested NRs formation mechanism; the OAI and the OAc are presented schematically in the figure, while the black dots represent the methylammonium and the brown rhombus represent the PbI.sub.2.

[0320] FIG. 7 provides HRTEM images of the NPs made of octyl/dodecyl/octadecyl ammonium iodide. Each couple of two vertical images presents particles of the same ligand, while the magnification is larger at the bottom image (see the scale bar).

[0321] FIGS. 8A-D provide: FIG. 8A—absorption spectra of the particles prepared using octyl/dodecyl/octadecyl ammonium iodide. FIG. 8B—PL spectra of the particles. FIG. 8C—an image of the particles under white light. FIG. 8D—an image of the particles under UV light (λ=254 nm).

[0322] FIG. 9 provides HRTEM images of the NPs made of octyl/dodecyl/octadecyl ammonium bromide. Each couple of two vertical images presents particles of the same ligand, while the magnification is larger at the bottom image (see the scale bar).

[0323] FIGS. 10A-D provide: FIG. 10A—absorption spectra of particles prepared using octyl/dodecyl/octadecyl ammonium bromide. FIG. 10B—PL spectra of the particles prepared using octyl/dodecyl/octadecyl ammonium bromide. FIG. 10C—an image of the particles under white light. FIG. 10D—an image of the particles under UV light (λ=254 nm).

DETAILED DESCRIPTION OF EMBODIMENTS

[0324] This invention provides facile low temperature synthesis of 2D perovskite nanorods in the structure (C.sub.8H.sub.17NH.sub.3).sub.2(CH.sub.3NH.sub.3).sub.2Pb.sub.3(I.sub.xBr.sub.1-x).sub.10, 0>x>1. The NRs were characterized by XRD, ED, and FFT analysis. The absorbance and the PL of the NRs show a shift to higher energies compared with the bulk materials. In addition, changing the halide composition enables tunability of the NRs band gap. Various ligands ratios were studied and analyzed by high-resolution transmission electron microscopy (HR-TEM), which assisted in revealing the formation mechanism of these novel 2D perovskite NRs.

[0325] FIG. 1 presents TEM images of the synthesized 2D perovskite NRs of the structure R.sub.2(CH.sub.3NH.sub.3).sub.n□1M.sub.nX.sub.3n+1 where (R═octylammonium, OA, being C.sub.8H.sub.17NH.sub.3, CH.sub.3NH.sub.3=MA, M=Pb, X=I, Br, 0<n<3). The halide composition did not affect the shape and the size of the nanorods; the average size of the nanorods was 2.25 nm 0.3 nm (width) and 11.36 nm±2.4 nm (length). The crystallographic structure of the NRs was analyzed using FFT as indicated in the insets provided in the images.

[0326] HRTEM images of the nanorods are shown in FIGS. 2A-D.

[0327] Table 1 shows the d-spacing values which were taken from the FFT analysis and the corresponding Miller indices for the various compositions. The crystallographic characterizations show that the perovskite NRs have tetragonal structure. It can be observed that the introduce of the Br ions into the perovskite structure changes the lattice parameters from a=b=8.856 Å, c=12.674 Å for (OA).sub.2(MA).sub.2Pb.sub.3I.sub.10 to a=b=8.611 Å, c=12.234 Å for (OA).sub.2(MA).sub.2Pb.sub.3(I.sub.xBr.sub.1-x).sub.10 (I>Br), a=b=8.484 Å, c=12.294 Å for (OA).sub.2(MA).sub.2Pb.sub.3(I.sub.xBr.sub.1-x).sub.10 (I<Br) and a=b=8.474 Å, c=11.943 Å for pure (OA).sub.2(MA).sub.2Pb.sub.3Br.sub.10 as described previously for bulk perovskite where the lattice parameter changes due to the smaller ionic radius of the Br.sup.− compared with I.sup.−.

[0328] The optical characterizations of the 2D perovskite NRs are presented in FIG. 4, including absorbance and PL; FIGS. 4B and 4C, respectively. The absorbance spectra of the various compositions are not similar to the absorbance of the bulk perovskite with the same compositions. MAPbI.sub.3 and MAPbBr.sub.3 bulks absorb until ˜800 nm and until ˜550 nm, respectively, while the (OA).sub.2(MA).sub.2Pb.sub.3I.sub.10 NRs and (OA).sub.2(MA).sub.2Pb.sub.3Br.sub.10 NRs absorb only until ˜650 nm and ˜530 nm, respectively (FIG. 4B).

TABLE-US-00001 TABLE 1 crystallographic data of the different NRs compositions, extracted from FFTs (see FIG. 1 inset). C.sub.8H.sub.17NH.sub.3 = OA, CH.sub.3NH.sub.3 = MA (OA).sub.2(MA).sub.2Pb.sub.3(I.sub.xBr.sub.1−x).sub.10, (OA).sub.2(MA).sub.2Pb.sub.3(I.sub.xBr.sub.1−x).sub.10, (OA).sub.2(MA).sub.2Pb.sub.3I.sub.10 I > Br I < Br (OA).sub.2(MA).sub.2Pb.sub.3Br.sub.10 d-spacing d-spacing d-spacing d-spacing (Å) (hkl) (Å) (hkl) (Å) (hkl) (Å) (hkl) 1.81 (404) 2.55 (312) 1.82 (404) 1.76 (226) 2.55 (312) 3.15 (004) 2.56 (312) 2.54 (312) 2.80 (310) 3.12 (220) 3.18 (004) 3.12 (220) 3.15 (004) 3.17 (004)

[0329] The difference in the absorbance is attributed to two main contributions. The first is related to the use of octylammonium as a ligand in the NRs synthesis. The octylammonium is a larger cation than the methylammonium and cannot incorporate into the perovskite structure. Therefore, the octylammonium is attached through its alkyl chain to the perovskite and limited the crystal growth in this direction (Additional details regarding the growth mechanism of these NRs are discussed below). Since the perovskite growth is limited, the perovskite NRs are formed in the 2D perovskite structure which implies a shift in the absorbance and PL to shorter wavelength (higher energies) and hence to larger band gaps.

[0330] The second contribution is related to the halide exchange when introducing Br into the (OA).sub.2(MA).sub.2Pb.sub.3I.sub.10 NRs. The Br(4p) orbitals with the Pb(6s) orbitals determined the absorbance peak, which is related to the valence band. The conduction band of PbI.sub.2 is composed of Pb(6p) orbitals, while its valence band composed of Pb(6s) orbitals and I(5p) orbitals. It was shown that the transitions in PbI.sub.2 are similar to the transitions in MAPbI.sub.xBr.sub.3-x (0>x>3). Further, the energy level of Br(4p) orbitals is lower in energy than Pb(6s) orbitals; therefore, the peak position of (OA).sub.2(MA).sub.2Pb.sub.3(I.sub.xBr.sub.1-x).sub.10, 0>x>1 is influenced and shifted to higher energy. This shift can be observed in FIGS. 4B and 4C when the increase in the Br concentration shifts the absorbance and the PL to higher energies. FIG. 4A shows the visual emission from the (OA).sub.2(MA).sub.2Pb.sub.3(I.sub.xBr.sub.1-x).sub.10 NRs in various compositions (0>X>1), from pure iodide to pure bromide. It can be observed that the pure (OA).sub.2(MA).sub.2Pb.sub.3I.sub.10 has a red emission supporting the PL and the Eg measurements.

[0331] Tauc plots were recorded for the NRs samples to calculate the energy band gaps (E.sub.g) of these nano materials. Tauc plots are given in FIG. 5, and their values are presented in FIG. 4D. As in the case of the bulk methylammonium lead halide perovskite, the Br concentration increases the materials' E.sub.g. However, the 2D perovskite NRs E.sub.g are in the range of 1.9 eV-2.26 eV with variation from the bulk methylammonium lead halide perovskite.

[0332] The PL-QY of the various NRs compositions is presented in FIG. 4D. The PL-QY is close to 30% for the (OA).sub.2(MA).sub.2Pb.sub.3I.sub.10 NRs and for the (OA).sub.2(MA).sub.2Pb.sub.3(I.sub.xBr.sub.1-x).sub.10 (I>Br) NRs. When the Br concentration is increased, the PL-QY decreased. Feldmann et al. have reported similar PL-QY for the perovskite nanostructures they studied. PL-QY of 20% was demonstrated for MAPbBr.sub.3 nanoparticles synthesized in a medium of alkyl-amine that controls the particle growth, and Hassan et al. measured 20% QY for 2D perovskite NPs.

[0333] The main factor influencing the formation of the NRs is the organic moieties present in the synthesis. Three organic molecules are used in the synthesis, methylammonium iodide/bromide (MAI/MABr), octylammonium iodide (OAI) and oleic acid (OAc). The long chain of the octylammonium iodide cannot be incorporated into the perovskite crystal. Instead it attached to specific sites on the perovskite surface inhibiting the growth in a particular direction. In addition, the presence of OAc in the synthesis solution plays a role in the formation of the NRs as discussed below. To elucidate the formation mechanism of these 2D perovskite NRs, the ratio of OAc to OAI was studied. Different molar ratios of ligands (OAI and OAc) were studied while keeping all other conditions constant (see Experimental Section).

[0334] The ratio of the OAI/OAc for the NRs discussed in this work is OAI/OAc=0.186. Therefore, ratios of 100% OAc, OAI/OAc=0.075 (lower than the standard ratio), OAI/OAc=0.250 (higher than the standard ratio) and 100% OAI were investigated.

[0335] TEM micrographs were recorded for the OAI/OAc ratios (FIGS. 6A-E). For 100% OAc (without OAI in the solution), there was no indication of the formation of QDs; the perovskite was formed as a bulk which precipitated to the bottom of the vial (FIG. 6A shows empty TEM grid). For OAI/OAc=0.075, the formation of QDs was observed, although their concentration was low (FIG. 6B). Where higher ratios were studied, e.g. OAI/OAc=0.250, mixed QDs and NRs were observed, indicated in FIG. 6D; and for 100% OAI, a high concentration of QDs was observed (FIG. 6E).

[0336] These results propose the following mechanism. At 100% OAc, no QDs were observed, which means that the OAc could not inhibit the perovskite growth. However, at 100% OAI, a high concentration of QDs was observed, suggesting that the OAI inhibits perovskite growth and attached strongly to the perovskite surface. The presence of iodide in the OAI assisted in the attachment of this alkyl chain to the QDs/NRs perovskite surface. When varying the ratio to 0.250 (excess of OAI relative to the standard), QDs and NRs are formed, indicated by the two images in FIG. 4D which were taken from the same sample. For a ratio of 0.075 (excess of OAc relative to the standard), the formation of NRs were rare. Therefore, it can be concluded that the OAI is attached to the NRs surface, while the OAc has an important role by shaping these QDs into NRs. The OAI attachment is much stronger to the NRs surface than that of the OAc since it fills the octahedral hole. The NRs are formed by the addition of monomers along specific axis, while the other axes length are blocked by high affinity ligands absorbed to the surface (FIG. 6F). The presence of the two ligands is essential for the formation of the NRs. As discussed, the OAI has higher affinity to the perovskite surface than the OAc, so that for OAI/OAc=0.075, there are not enough OAI ligands to allow the formation of NRs (and even the QDs formation is low). When the ratio was increased to OAI/OAc=0.250 with an excess of OAI, some NRs were formed with a high concentration of QDs due to the stabilization of the QDs by the OAI, but the low concentration of OAc results in the formation of few NRs. Therefore, pure NRs formation is achieved only when there is a balanced ratio of OAI/OAc=0.186. On one hand, there is enough OAI to stabilize the NRs perovskite surface, and on the other hand, enough OAc to balance the growth into NRs shape.

CONCLUSIONS

[0337] This invention provides perovskite nanorods and nanocubes, such as those having the structure (C.sub.8H.sub.17NH.sub.3).sub.2(CH.sub.3NH.sub.3).sub.2Pb.sub.3(I.sub.xBr.sub.1-x).sub.10, 0>x>1, which were synthesized by facile low temperature synthesis. The perovskite NRs show high PL with very good size distribution. Their bang gap can be tuned by halide exchange varying between 1.9 eV-2.26 eV. The wider band gap observed for these NRs might be related to the characteristic of their 2D structure, due to the use of OAI in their synthesis. XRD, ED, and FFT provide evidence for the crystallographic structure of these NRs. Studying different ligand ratios (OAI/OAc) of the NRs revealed their formation mechanism. These 2D perovskite NRs have excellent potential to be used in variety of optoelectronic applications.

EXPERIMENTAL

[0338] Precursor synthesis. Octyl ammonium iodide (OAI) was synthesized by reacting 1 mL of octylamine (99%, Sigma) with 2 mL of hydroiodic acid (57 wt % in water, Aldrich) and 14 mL of distilled water in 100 mL round bottom flask at 0° C. for 2 hr while stirring. The precipitate was recovered by evaporating the solvents at 50° C. using a rotary evaporator. The white raw product was washed with diethyl ether. The washing step was repeated several times. After filtration, the solid was collected and dried at 60° C. in a vacuum oven for 24 hr.

[0339] Methyl ammonium iodide/bromide (MAI/MABr) was synthesized by reacting 27.8 mL of methylamine (40% in methanol, TCI) with 30 mL of hydroiodic acid (57 wt % in water, Aldrich) or 23.32 mL of hydrobromic acid (48 wt % in water, Aldrich) in a 250 mL round bottom flask at 0° C. for 2 hrs while stirring. The precipitate was recovered by evaporating the solvents at 50° C. using a rotary evaporator. The white raw product was washed with diethyl ether. The washing step was repeated several times. After filtration, the solid was collected and dried at 60° C. in a vacuum oven for 24 hr.

[0340] NRs synthesis. 1M PbI.sub.2/PbBr.sub.2 (99%, Aldrich) and 0.63M MAI/MABr/MAI:MABr=1:1 solutions in DMF (Aldrich) were prepared under nitrogen atmosphere. The solutions were heated on a hot plate at 83° C. until fully dissolved. 15 mg OAI and 100 μL oleic acid (technical grade, 90%, Aldrich) were mixed with 2 mL octadecene (technical grade, 90%, Aldrich) in a small vial for an hour. Then 100 μL of the 0.63M MAI/MABr/MAI:MABr=1:1 solutions in DMF were added, followed by the addition of 50 μL of 1M PbI.sub.2/PbBr.sub.2 solution. Finally, 5 mL of chloroform (biolab) were added. The vial was centrifuged at 3000 rpm for 1 minute. Then the liquid phase was transformed into a clean vial, and again centrifuged for 5 minutes at 6000 rpm. In the case of various ligand compositions, the syntheses include the following ratio OAI/OAc: 100% OAc, 0.075, 0.186, 0.250 and 100% OAI.

[0341] Characterization. Transmission electron microscopy (TEM) and electron diffraction (ED) observations were carried out using a Tecnai F20 G2 (FEI Company, USA). The samples were prepared as follows: 3 μL drop of the NRs dispersion was placed on a copper grid coated with amorphous carbon film, followed by evaporation of the solvent by a vacuum pump. FFT was done using the program “digital micrograph”. Absorption spectra were recorded using Jasco V-670 spectrophotometer. Photoluminescence (PL) measurements were performed using L shaped spectrophotometer (Edinburgh Instruments FL920). The samples were excited using at 400 nm. The emission was collected in 90 degrees at the range of 450-800 nm. Photoluminescence quantum yields (PL-QY) were measured using Hamamatsu absolute PL-QY spectrometer C11347. Transmission (for the Tauc plots) spectra was measured using Varian Cary 5000 UV-vis-NIR spectrophotometer. X-ray powder diffraction measurements were performed in grazing incidence X-ray diffraction (GIXRD) mode on the D8 Advance Diffractometer (Bruker AXS, Karlsruhe, Germany) with a goniometer radius of 217.5 mm, a secondary graphite monochromator, 2° Soller slits and a 0.2 mm receiving slit. XRD patterns within the range 5° to 60° 2θ were recorded at room temperature using CuKa radiation (1¼ 1.5418° A) with the following measurement conditions: tube voltage of 40 kV, tube current of 40 mA, step-scan mode with a step size of 0.02° 2θ and counting time of 1-3 s per step. The value of the grazing incidence angle was 2.5°.

[0342] Processes for the Preparation of Nanoparticles of the Invention—

[0343] The NPs of the invention, may be prepared as follows: [0344] preparing separate precursor's solution(s), e.g., under inert conditions, and causing solubilization of the precursor materials; [0345] mixing the precursor's solutions under conditions permitting formation of the nanoparticles, the conditions being as defined herein; and [0346] optionally separating the thus obtained nanoparticles.

[0347] For some applications, the nanoparticles are separated and used, while for other applications, the medium containing the nanoparticles may be used as prepared.

[0348] In an exemplary procedure, nanoparticles of the invention were formed as follows: [0349] 1) PbI.sub.2 or PbBr.sub.2 in a solvent was prepared. [0350] 2) MAI or MABr in a solvent was prepared. [0351] 3) The solutions were mixed together and the mixture was permitted to form nanopartciles. [0352] 4) The nanoparticles were isolated or maintained in the medium.

[0353] Alternatively, the following process was utilized: [0354] 1) A solution of PbI.sub.2 or PbBr.sub.2 in dimethylformamide (DMF) was prepared. 2) A solution of MAI or MABr in DMF was prepared. [0355] 3) A solution of octylammonium iodide (OAI), oleic acid (OAc) and octadecene was prepared. [0356] 4) The three solutions were combined and allowed to form nanoparticles.

[0357] Under specific conditions, the following were used: [0358] 1) A solution of PbI.sub.2 or PbBr.sub.2 in dimethylformamide (DMF) was prepared. The solution was heated at 80° C.-85° C. [0359] 2) A solution of MAI or MABr in DMF was prepared. The solution was heated at 80° C.-85° C. [0360] 3) A solution of octylammonium iodide (OAI), oleic acid (OAc) and octadecene were formed at 80° C. [0361] 4) The MAI/MABr/mixture of both solutions in DMF was added to the mixture of OAI+OAc+octadecene at 80° C. [0362] 5) The mixture was centrifuged to afford the nanoparticles.

[0363] In an exemplary method: [0364] 1) 1M solution of PbI.sub.2 or PbBr.sub.2 in dimethylformamide (DMF) was prepared under N.sub.2 atmosphere conditions. The solutions were placed on a hot-plate at 80° C.-85° C. until they were clear. [0365] 2) 0.63M solution of MAI or MABr in DMF was prepared in N.sub.2 glovebox. For the mixture perovskite preparation, solution of MAI+MABr in DMF as prepared, so that the total molar concentration as 0.63M, for example: 250 μL of 0.315M solution of MAI in DMF was mixed with 250 μL of 0.315M solution of MABr in DMF. The solutions were placed on a hot-plate at 80° C.-85° C. until they were clear. [0366] 3) 0.015 g of octylammonium iodide (OAI)+100 μL of oleic acid (OAc)+2 mL of octadecene were mixed at 400 rpm at 80° C. for about 1 hour. [0367] 4) 100 μL of the above MAI/MABr/mixture of both solution in DMF was added to the mixture of OAI+OAc+octadecene while mixing at 400 rpm and heating at 80° C. 50 μL of the above 1M PbI.sub.2/PbBr.sub.2 solution in DMF was added afterwards. The mixture was left for 1 minute of mixing at 400 rpm under heating (80° C.), and then 5 mL of chloroform were added (the temperature of the chloroform was room temperature). Color varied from clear bright yellow to the perovskite color (depending on the halides which were used). [0368] 5) The mixture was centrifuged at 3000 rpm for 1 minute. Then the liquid was moved to a clean vial, and again centrifuged at 6000 rpm for about 5 minutes. The clear solution contained the nanorods.

[0369] TEM of the obtained nanorods:

TABLE-US-00002 TABLE 2 Electron diffraction results of (C.sub.8H.sub.17NH.sub.3).sub.2(CH.sub.3NH.sub.3).sub.2Pb.sub.3I.sub.10, NRs: d-spacings and their corresponding Miller indices. d-spacing (±0.04 Å) hkl 3.108 (220) 1.743 (226) 1.888 (422)