HALIDE ABX3 PEROVSKITE PARTICLES AND THEIR APPLICATION IN CONTROLLING PHOTO-FLUX

Abstract

A light valve containing ABX.sub.3 perovskite particles (200) suspended in a liquid suspension (300) that can control light transmittance is provided. The preferable ABX.sub.3 perovskite particles (200) are halide ABX.sub.3 perovskite particles wherein A is at least one of Cs.sup.+, CH.sub.3NH.sub.3.sup.+, and Rb.sup.+, B is at least one of Pb.sup.2+, Ge.sup.2+, and Sn.sup.2+, and X is at least one of Cl.sup., Br.sup., and I.sup.. Use of the light valve in the manufacture of a light control device and a method of controlling light transmittance by using the light valve are also provided.

Claims

1. (canceled)

2. A light valve, comprising a first layer of a transparent conductive substrate; an active layer containing ABX.sub.3 perovskite particles suspended in a liquid suspension; and a second layer of a transparent conductive substrate, wherein the ABX.sub.3 perovskite particles are halide ABX.sub.3 perovskite particles, and wherein A is at least one of Cs.sup.+, CH.sub.3NH.sub.3.sup.+, and Rb.sup.+; B is at least one of Pb.sup.2+, Ge.sup.2+, and Sn.sup.2+; and X is at least one of Cl.sup., Br.sup., and I.sup..

3. The light valve as recited in claim 2, wherein A is at least one of Cs.sup.+ and CH.sub.3NH.sub.3.sup.+; B is Pb.sup.2+; and X is at least one of Br.sup. and I.sup..

4-6. (canceled)

7. The light valve as recited in claim 1, wherein the halide perovskite particles are uniformly dispersed in the liquid suspension.

8. The light valve as recited in claim 7, wherein the liquid suspension is capable of maintaining the suspended ABX.sub.3 perovskite particles in gravitational equilibrium.

9-13. (canceled)

Description

BRIEF DESCRIPTION OF DRAWINGS

[0026] FIG. 1 presents schematically a light controlling device, wherein, a liquid suspension (300) is sandwiched between two transparent substrates (100) and (100). The halide ABX.sub.3 perovskite particles (200) are suspended in the liquid suspension (300).

[0027] FIG. 2 presents light transmittance of a light valve (LV) device made according to this invention Example 6 before and after applying an electric voltage of 220V

[0028] FIG. 3 presents the cell structure of the ABX.sub.3 perovskite.

DETAILED DESCRIPTION

[0029] The present invention provides a new form of perovskite particles and the method to use them to control the flux of light in a light control device, or referred as a light valve.

[0030] FIG. 1 presents schematically a light controlling device, wherein, a liquid suspension (300) is sandwiched between two transparent substrates (100) and (100). The halide ABX.sub.3 perovskite particles (200) are suspended in the liquid suspension (300). In the absence of an applied electrical field (OFF state), the halide ABX.sub.3 perovskite particles in the liquid suspension assume random positions due to Brownian movement. Hence, a beam of light passing into the light valve is absorbed/scattered. The light valve is thus relatively dark in the OFF state. When an electric field is applied thereto (ON state), the light control halide ABX.sub.3 perovskite particles are polarized, thereby being arranged in directions parallel to each other in accordance with the electric field, and most of the light can pass through the cell. The light valve is thus relatively transparent in the ON state.

[0031] The present invention provides a new use of ABX.sub.3 perovskite particles, and method to make such a material. The present invention further provides a light valve, comprising a liquid suspension having ABX.sub.3 perovskite particles, which can electronically control transmission of light. More specifically, for the ABX.sub.3 perovskite particles, A is at least one of Cs.sup.+, CH.sub.3NH.sub.3.sup.+, and Rh.sup.+, B is at least one of Pb.sup.2+, Ge.sup.2+, and Sn.sup.2+, and X is at least one of Cl.sup., Br.sup., and In case that X is at least one of Cl.sup., Br.sup., and I.sup., the ABX.sub.3 perovskite particles are also referred to as halide ABX.sub.3perovskite particles. Sill more preferably, A is at least one of Cs.sup.+ and CH.sub.3NH.sub.3.sup.+, B is Pb.sup.2+, X is at least one of Br.sup. and I.sup..

[0032] Preferably, the halide ABX.sub.3 perovskite particles have a non-spherical morphology. The non-spherical morphology is at least one of the nanowires, nanorods (one-dimensional); nanosheets (two-dimensional); cuboids, irregular (three-dimensional) particles.

[0033] Particularly, the perovskite particles (including the halide ABX.sub.3 perovskite particles) have a morphology of nanorods. Preferably, for the nanorods, it has a. length of 50 nm-2000 nm, more preferable 200 nm -500 nm, and a thickness or diameter of 20 nm-200 nm, more preferable 50 nm-100 nm. Preferably, for the nanorods, the ratio of length:thickness or length:diameter is above 3:1, 4:1, 5:1, 6:1, 8:1 or 10:1. Preferably, the ratio of length:thickness or length:diameter is 3:1 to 20:1, more preferably 8:1 to 15:1. Preferably, the perovskite particles (including the halide ABX.sub.3 perovskite particles) have a morphology of nanorods which have a length of 50 nm-2000 nm, a thickness or diameter of 20 nm-200 nm and a ratio of length:thickness or length:diameter above 3:1. Preferably, the perovskite particles (including the halide ABX.sub.3 perovskite particles) have a morphology of nanorods which have a length of 50 nm-2000 nm, a thickness or diameter of 20 nm-200 nm and a ratio of length:thickness or length:diameter of 8:1 to 15:1. More preferably, the perovskite particles (including the halide ABX.sub.3 perovskite particles) have a morphology of nanorods which have a length of 200 nm-500 nm, a thickness or diameter of 50 nm-100 nm and a ratio of length:thickness or length:diameter of 8:1 to 15:1.

[0034] In the disclosure, the length, thickness or diameter means an average length, an average thickness or an average diameter, respectively.

[0035] As illustrated in FIG. 1, the ABX.sub.3 perovskite particles (200) which are encapsulated inside the said liquid suspension (300) shall be capable of re-orientating themselves in an electronic field. In terms of geometric dimensions, the ABX.sub.3 perovskite particles are preferably in a form of nanorods having an average length of about 50 nm-2000 nm, and an average thickness or diameter of 20 nm-200 nm, and a ratio of length:thickness or length:diameter above 3:1, preferably 8:1 to 15:1.

[0036] According to this invention, the liquid suspension (300), which is used as a liquid medium to suspend the ABX.sub.3 perovskite particles, comprises one or more non-aqueous, electrically resistive liquids. Such a liquid or a liquid mixture, referring as the suspension medium, can maintain the suspended ABX.sub.3 perovskite particles in gravitational equilibrium.

[0037] More specifically in this invention, the liquid suspension (300) comprises one or more a mineral resistive oil, a synthetic resistive oil and a vegetable oil. Mineral resistive oils, such as transformer oils; synthetic resistive oils, such as silicone oils, fluorocarbon organic compounds, plasticizers (such as dioctyl phthalate, dibutyl phthalate, diisobutyl phthalate, triisodecyl trimellitate (TDTM), dodecylhenzene, polybutene oil; vegetable oils, such as castor oil, soybean oil, rapeseed oil, are good liquid suspension medium. Technically, the liquid suspension medium used in the light valve of the present invention can be any liquid light valve suspension known in the art and can be formulated according to techniques well known to those skilled in the art.

[0038] According to this invention as illustrated in FIG. 1, the said transparent electrode (100) can be made of the same material or different materials, where light can be transmitted through, preferably having a light transmittance equals to or greater than 80%, more preferably 90%. Either the said transparent electrode (100) can be ITO conductive glass, ITO/PET conductive film, Ag nano wire/PET conductive film, Cu nanowire/PET conductive film. The transparent electrode (100) are preferred to be of the same material for the simplicity of processing and for the same physical properties (such as flexibility and thermal expansion), important for device durability under certain conditions, such as thermal stress.

[0039] As ABX.sub.3 perovskite particles are sensitive to moisture and oxygen, the two transparent electrodes sandwiched by the liquid suspension can be sealed with a resistive material, such as epoxy resin, etc., which can be used to seal the sealing material around the two transparent electrodes. The light valve is driven by alternating current to adjust light transmittance, preferably 5-500V alternating current.

[0040] The invention will now be described in more detail with reference to the following examples. However, these examples are given for illustration only and are not intended to limit the scope of the present invention. All chemicals used in the examples are purchased from Sigma-Aldrich Company unless otherwise specified. In all these examples, all parts and percentages are by weight unless otherwise noted. The light transmittance and absorption spectrum of the LV device was measured by an Oceanview spectrometer.

EXAMPLE 1

Preparation of Cs-Oleate

[0041] Cs.sub.2CO.sub.3 (4.07 g) was loaded into a 250 mL, 3-neck flask along with octadecene (50 mL, ODE) and oleic acid (11.088 g), and the mixture was dried for 1 h at 12.0 C. and then heated under Ar to 150 C. until all Cs.sub.2CO.sub.3 reacted with oleic acid. Since Cs-Oleate precipitates out of ODE at room temperature, it has to be preheated to make it soluble before usage.

EXAMPLE 2

Synthesis of CsPbI.SUB.3 .Nanorods

[0042] N,N-dimethylformamide (100 mL, DMF) and PbI.sub.2 2.306 (5 mmol) were loaded into a 250 mL flask. Acetate acid 4.654g (77.5 mmol) and dodecylamine 0.797 g (4.3 mmol) were added. After complete solubilization of PbI.sub.2, 5 mL Cs-Oleate solution was added (prepared as described Example 1). Then, the hybrid solution was added into a 5 L flask along with 4200 mL toluene.

[0043] Then, centrifuge the reaction solution at 5000G for 1.5 hours and discard the supernatant to yield the light control CsPbI.sub.3.

[0044] Then, the CsPbI.sub.3 were further dispersed with 500 mL of toluene, mixed well with shaking and sonication (referring as LCP-Example-2).

EXAMPLE 3

Synthesis of CsPbBr.SUB.3 .Nanorods

[0045] In the same manner as in Example 2, only 1.835 g of PbBr.sub.2 was used instead of 2.306 g of PbI.sub.2. A toluene mixture containing CsPbBr.sub.3 is referring as LCP-Example-3.

EXAMPLE 4

Preparation of LV Suspension Containing CsPbI.SUB.3 .Nanorods

[0046] In the 250 ml round bottom glass flask was weighted 10 g of TDTM (triisodecyltrimellitate), and the LCP-Example-2 prepared in the Example 2 was added in portions. After thoroughly mixing by shaking, toluene was subsequently removed by a rotary evaporator for 3 hours at 80 C. to yield a LV suspension containing CsPbI.sub.3 referred as LV Suspension Example-4.

EXAMPLE 5

Preparation of LV Suspension Containing CsPbBr.SUB.3.Nanorods

[0047] In the 250 ml round bottom glass flask was weighted 15 g of silicone oil, and the LCP-Example-3 prepared in the Example 3 was added in portions. After thoroughly mixing by shaking, toluene was subsequently removed by a rotary evaporator for 3 hours at 80 C. to yield a IV suspension containing CsPbBr.sub.3 referred as IV Suspension Example-5.

EXAMPLE 6

LV Devices Made from LV Suspension-Example-4

[0048] In this example, a wet thickness of 200 um of the IX Suspension-Example 4 made in Example 4 was sealed between two transparent electrodes of ITO conductive glass using epoxy resin to produce a light valve referring as LV Device-6. When no electric voltage is applied (OFF State), LV Device-6 exhibits an orange tint and light transmission is measured to be 4.7%. When it was electrically activated using 220 Volts AC at 50 Hz (ON State), the LV Device-6 turns clearer and light transmission is measured to be 25.6%. FIG. 2 presents the absorption spectrum of LV Device-6 at OFF state and ON state respectively.

EXAMPLE 7

LV Devices Made from LV Suspension-Example-5

[0049] In this example, a wet thickness of 180 um of the LV Suspension-Example 5 made in Example 5 was sealed between two transparent electrodes of ITO conductive glass using epoxy resin to produce a light valve referring as LV Device-7. When no electric voltage is applied (OFF State), LV Device-7 exhibits an orange tint and light transmission is measured to be 6.4%. When it was electrically activated using 220 Volts AC at 50 Hz (ON State), the LV Device-7 turns clearer and light ransmission is measured to be 30.2%.

TABLE-US-00001 TABLE 1 Typical performance of LV devices Transmittance % LV Device Off state On state LV Device-6 4.7 25.6 LV Device-7 6.4 30.2