Perovskite electro-optical modulator and preparation method thereof

Abstract

The invention specifically discloses a light beam deflector based on a perovskite electro-optical effect and a preparation method thereof, and relates to the technical field of photoelectricity, and the device comprises a laminated structure composed of a period-adjustable strip-shaped ITO electrode array constructed on a transparent substrate, a perovskite single crystal film and a top gold electrode. Through the low half-wave voltage characteristic (Vpi < 5V) of a perovskite single crystal material, when a periodic driving voltage is applied between an ITO electrode and a gold electrode, a perovskite layer is induced to generate a spatial gradient refractive index change, so that a blazed grating-like phase modulation effect is formed, and non-mechanical deflection control of an incident beam within a range of + / -30 degrees is realized. The light beam deflector has the characteristics of wide spectral response, high response speed and low working voltage, can be applied to laser radar beam control, space optical communication link calibration and holographic display systems, and provides a miniaturized and low-cost dynamic light beam control solution for a new generation of photoelectric integrated equipment.

Description

Technical Field

[0001] The present invention relates to the field of beam deflection, and particularly to a perovskite beam deflector and a preparation method thereof. Background Art

[0002] As a core part of optical field regulation, beam deflection technology has important application values in fields such as lidar, free-space optical communication, and laser processing. Traditional mechanical deflection systems rely on rotating polygonal mirrors or galvanometric mirrors to achieve beam scanning, and have inherent defects such as large volume, slow response speed (millisecond level), and poor vibration resistance. In recent years, the developed non-mechanical deflection technologies mainly include the electro-control scheme based on liquid crystal on silicon (LCoS) and the electro-optic deflection device based on lithium niobate (LiNbO 3 ) crystal. However, liquid crystal devices are limited by the molecular rotation relaxation time, and the response speed is usually limited to the kilohertz level, and there are problems such as high operating voltage (>20V) and low optical damage threshold; while lithium niobate devices have a response speed in the microsecond level, but their electro-optic coefficient is relatively low (γ 33 ≈30 pm / V), resulting in a driving voltage as high as the order of hundreds of volts required to achieve π-phase modulation, seriously restricting the device integration and energy efficiency ratio.

[0003] In recent years, organic-inorganic hybrid perovskite materials have attracted wide attention due to their excellent optoelectronic properties. Their electro-optic coefficient is better than that of lithium niobate, and they have advantages such as high carrier mobility (>100 cm 2 / (V·s)) and good solution processability. However, the existing research on perovskite-based electro-optic devices mostly focuses on bulk single crystal modulators. Their practical applications face the following key bottlenecks: bulk single crystal devices mostly adopt a transverse electric field modulation structure (the light propagation direction is parallel to the electrode surface), resulting in insufficient electric field action depth and light field mode overlap efficiency. Even using the high electro-optic coefficient characteristics, a driving voltage of 30 - 50V still needs to be applied to achieve π-phase modulation, which is difficult to be compatible with 5V-level CMOS driving circuits. The thermal conductivity of perovskite bulk single crystal is only 0.5 W / mK, and significant thermo-optic lens effects are generated under the irradiation of high-power lasers (>5 mW / cm 2 ), causing fluctuations in optical path difference and wavefront distortion. The continuous accumulation of photoinduced hot carriers during operation will also lead to non-linear attenuation of the electro-optic coefficient. Summary of the Invention

[0004] Technical Problem: Aiming at the problems of high driving voltage, limited response speed, and insufficient thermal stability existing in the existing non-mechanical beam deflection devices, the present invention proposes a low-voltage, high-dynamic beam deflector based on the electro-optic effect of perovskite and a preparation method thereof. By optimizing the electrode structure and thin film growth process, the bottleneck of the electric field-light field coupling efficiency of traditional perovskite bulk single crystal devices is broken through, and efficient phase modulation compatible with CMOS driving circuits is realized.

[0005] Technical solution: A beam deflector based on the electro-optic effect of perovskite of the present invention includes:

[0006] A patterned ITO strip electrode array on a transparent substrate, with an electrode spacing of 50-200 μm;

[0007] An ABX 3 Perovskite single crystal thin film disposed on the ITO strip electrode, with a chemical general formula of ABX 3 , where A = Cs / FA / MA; X = Cl - , Br - , I - ; B = Pb 2+ / Sn 2+ , with a thickness of 5-100 μm;

[0008] A top metal electrode covering the perovskite;

[0009] A PCB driving substrate bonded to the ITO electrode, containing a periodic voltage output circuit module; where the PCB driving substrate includes 8 metal electrodes, and the ITO electrode is bonded to the metal electrode through a gold wire.

[0010] For the described beam deflector, the period Λ of the ITO electrode array satisfies Λ = λ / sinθ, where λ is the working wavelength of 400-800 nm, and θ is the target deflection angle of 10°-30°;

[0011] Each period contains 4-16 voltage-dividing electrodes, and the voltage difference ΔV between adjacent electrodes is ΔV = 2V π / N, V π is the half-wave voltage of the perovskite thin film, and N is the number of voltage-dividing electrodes.

[0012] A periodic square wave voltage of 0-10 V is applied between the ITO and the gold electrode to induce a refractive index gradient change of Δn≥0.01 in the perovskite layer; the target deflection angle θ is regulated by the formula θ = arcsin(mλ / Λ), where m = +1 and the diffraction efficiency > 65%.

[0013] The preparation method of the beam deflector based on the electro-optic effect of perovskite of the present invention includes the following steps:

[0014] Step 1. Preparation of the precursor solution: Dissolve PbX 2 and AX with a molar ratio of 1:1 in a DMF solvent to prepare a perovskite precursor solution with a concentration of 0.5-1.5 M of ABX 3 ;

[0015] Step 2. Preparation of single crystal film: Inject the above precursor solution into the gap between two glass substrates with patterned ITO strip electrode arrays and an ITO spacing of 5 - 75 μm, form a confined space through a 10 - 100 μm thick spacer, and perform thermal annealing at 60 - 100 °C for 48 - 168 hours to obtain a single crystal thin film;

[0016] Step 3. Electrode integration: Deposit a 30 - 100 nm metal electrode on the single crystal thin film by electron beam evaporation process, and bond the ITO electrode lead to the PCB substrate by gold wire ball bonding;

[0017] Step 4. Encapsulation treatment: Coat the edge of the single crystal thin film with ultraviolet curable epoxy resin to form a moisture-proof sealing structure.

[0018] In the above Step 1: The ABX 3 perovskite single crystal thin film is MAPbCl 3 , MAPbBr 3 , MAPbI 3 .

[0019] In the above Step 2: The thickness of the confined space is regulated by a polyimide spacer, and the tolerance ≤ ±5 μm.

[0020] In the above Step 3: The electrode integration is one of the electron beam evaporation process and the magnetron sputtering process, and the electrode material includes one of gold, silver, platinum, titanium, aluminum, copper, ITO, and IZO.

[0021] The spacing of the ITO electrodes is 5 - 200 μm, and the number of leads is 2 - 16.

[0022] Beneficial effects: The above technical solution provided by this application has the following advantages compared with the prior art:

[0023] (1) Low voltage drive: Utilize the high electro-optic coefficient (γ > 50 pm / V) of the perovskite single crystal thin film and the longitudinal electric field loading structure, the half-wave voltage V π < 5V, which is reduced by more than 10 times compared with lithium niobate devices;

[0024] (2) High dynamic performance: The carrier mobility > 100 cm 2 / (V·s), the response speed reaches the microsecond level, and supports kHz-level beam scanning;

[0025] (3) Excellent thermal stability: The film structure improves the heat dissipation ability (the thermal conductivity is increased to 1.2 W / mK), tolerates > 10 MW / cm 2 laser irradiation, and the working temperature range is extended to -40 °C to +85 °C;

[0026] (4) High integration: The device unit size ≤ 5 × 5 mm 2, supporting 64×64 array integration (duty cycle > 85%), suitable for miniaturized optoelectronic systems. Description of the Drawings

[0027] Figure 1 Optical picture of the MAPbBr 3 single crystal thin film prepared in Example 1 of the present invention.

[0028] Figure 2 Absorption&PL spectra of the MAPbBr 3 single crystal thin film in Example 1 of the present invention.

[0029] Figure 3 XRD spectra of the MAPbBr 3 single crystal thin film in Example 1 of the present invention.

[0030] Figure 4 Schematic diagram of the device of the beam deflector of the present invention. Among them are: ITO strip electrode array 1, ABX 3 perovskite single crystal thin film 2, top metal electrode 3, PCB driving substrate 4, metal electrode 5, gold wire 6.

[0031] Figure 5 Simulation effect diagram of the diffraction angle and the number of electrodes in a single period of the beam deflector of the present invention.

[0032] Figure 6 Simulation effect diagram of the relationship between the diffraction efficiency and the diffraction angle of the beam deflector of the present invention. Detailed Implementation Modes

[0033] To make the substantial features and the practicality of the present invention more understandable, the technical solutions of the present invention will be further described in detail below in conjunction with the drawings and several specific embodiments. However, the following descriptions and explanations of the embodiments do not constitute any limitation to the protection scope of the present invention. Equivalent transformations or substitutions in terms of function, method, or structure made by those of ordinary skill in the art based on these embodiments all fall within the protection scope of the present invention:

[0034] A method for preparing a polarization detector based on the self-polarization effect of a perovskite heterojunction of the present invention includes the following steps:

[0035] Prepare ABX 3 perovskite precursor solution: Dissolve BX 2 and AX in an organic solvent to obtain ABX 3 perovskite precursor solution.

[0036] Prepare ABX 3 perovskite single crystal film: Prepare ABX 3The perovskite precursor solution is coated on two customized ITO glasses, and a polyimide spacer is placed between the two ITO glasses to control the film thickness. The corresponding temperature and time parameters are set, and the ABX 3 single crystal film is obtained by the solution space confinement method.

[0037] Electrode evaporation is performed on the ABX 3 single crystal film. The ITO electrode leads are bonded to the PCB substrate by gold wire ball bonding. The edges of the device are coated with ultraviolet curable epoxy resin to form a moisture-proof seal, and finally a perovskite electro-optic modulator is obtained.

[0038] Optionally, the ABX 3 perovskite single crystal film is MAPbCl 3 , MAPbBr 3 , MAPbI 3 , preferably MAPbBr 3 .

[0039] Optionally, the spacing of the ITO electrodes is 50-200 μm, and the number of leads is 2-16; preferably, the spacing of the ITO electrodes is 75 μm, and the number of leads is 8.

[0040] Optionally, in the process of preparing the ABX 3 perovskite single crystal film, the volume of the ABX 3 perovskite precursor solution is 70-200 μL, the heating temperature is 60-100 °C, and the heating time is 48-168 h; preferably, the ABX 3 perovskite precursor solution is 150 μL, the heating temperature is 75 °C, and the heating time is 72 h.

[0041] Optionally, the thickness of the polyimide spacer is 10-100 μm, preferably 30 μm.

[0042] Optionally, in the electrode evaporation, the evaporated electrode material is gold, the electrode thickness is 20-100 nm, preferably 30 nm.

[0043] In a second aspect, the present invention provides a perovskite electro-optic modulator prepared by the preparation method provided in the first aspect of the present invention:

[0044] When a periodic square wave voltage of 0-10 V is applied between the ITO and the top electrode, a spatial gradient refractive index change (Δn≥0.01) is formed in the perovskite layer, generating a blazed grating-like phase modulation effect; the beam deflection angle θ is regulated by the formula θ = arcsin(mλ / Λ) (m = +1 order diffraction efficiency > 65%), where Λ is the electrode period, satisfying Λ = λ / sinθ (λ = 400-800 nm, θ = 10°-30°).

[0045] Example 1

[0046] Preparation of MAPbBr 3 Experimental procedure of the beam deflector:

[0047] (1) Preparation of the precursor solution: Dissolve lead bromide and methylammonium bromide in N,N-dimethylformamide, stir in a beaker until completely dissolved, with a stirring rate of 800 rpm, and prepare a 1 M MAPbBr 3 perovskite precursor solution. Filter the solution using a 22 μm organic filter head to form a clear and transparent MAPbBr 3 precursor solution, and the molar ratio of lead bromide to methylammonium bromide is 1:1.

[0048] (2) Preparation of the single crystal film: Inject 150 μL of the precursor solution into the gap between two glass substrates with a patterned ITO strip electrode array and an ITO electrode spacing of 75 μm, and place a 30 μm thickness control spacer between the two ITO glasses to form a confined space. Anneal at 75 °C for 72 hours to obtain a single crystal thin film. The physical picture is as Figure 1 shown. The perovskite single crystal thin film obtained by the preparation method of the present invention has good optical transparency. The Absorption&PL spectra (as Figure 2 shown), XRD spectra (as Figure 3 shown) indicate that the prepared MAPbBr 3 single crystal thin film has good crystallinity;

[0049] (3) Electrode integration: Deposit a 30 nm metal electrode on the surface of the perovskite layer by vacuum evaporation, and bond the leads of 8 adjacent ITO electrodes under the MAPbBr 3 single crystal thin film to the PCB substrate by gold wire ball bonding;

[0050] (4) Encapsulation treatment: Coat the edge of the device with ultraviolet curable epoxy resin to form a moisture-proof sealing structure.

[0051] The final obtained MAPbBr 3 schematic diagram of the beam deflector is as Figure 4 shown.

[0052] Perform numerical simulation on the performance of the MAPbBr 3 beam deflector:

[0053] According to the given electrode period Λ = 150 μm, perform numerical simulation on the beam deflection effect of the device on incident light of 4 specific wavelengths (λ = 635, 808, 1550, 4000 nm). The relationships between the diffraction angle and the number of electrodes in a single period, and the diffraction efficiency and the diffraction angle are as Figure 5 and Figure 6As shown, for incident light of the same wavelength, as the number of electrodes within a single period increases, the beam deflection angle becomes smaller and the diffraction efficiency becomes higher.

[0054] Device unit size ≤ 5×5mm 2 ;

[0055] Supports 64×64 array integration, duty cycle > 85%; operating temperature range -40°C to +85°C.

Claims

1. A beam deflector based on the perovskite electro-optical effect, characterized in that: The beam deflector comprises: A patterned ITO strip electrode array (1) on a transparent substrate, with an electrode spacing of 50-200 μm; The ABX3 perovskite single crystal film (2) disposed on the ITO strip electrode has a general chemical formula of ABX3, wherein A=Cs / FA / MA; X=Cl - Br - ,I - ; B=Pb 2+ / Sn 2+ , thickness is 5-100μm; A top metal electrode (3) covering the perovskite; A PCB driving substrate (4) bonded to an ITO electrode contains a periodic voltage output circuit module; wherein the PCB driving substrate (4) contains eight metal electrodes (5), and the ITO electrodes are bonded to the metal electrodes (5) via gold wires (6).

2. The beam deflector based on the perovskite electro-optical effect according to claim 1, characterized in that: The beam deflector, the period Λ of the ITO electrode array satisfies Λ=λ / sinθ, where λ is the operating wavelength of 400-800nm, and θ is the target deflection angle of 10°-30°; A single cycle contains 4-16 voltage-dividing electrodes, and the voltage difference between adjacent electrodes is ΔV=2V π / N,V π is the half-wave voltage of the perovskite film, and N is the number of voltage-dividing electrodes.

3. The beam deflector based on the perovskite electro-optical effect according to claim 1, characterized in that: A 0-10V periodic square wave voltage is applied between the ITO and gold electrodes to induce a refractive index gradient change of Δn≥0.01 in the perovskite layer; the target deflection angle θ is controlled by the formula θ=arcsin(mλ / Λ), where m=+1 order diffraction efficiency>65%.

4. A method for preparing a beam deflector based on the perovskite electro-optical effect as claimed in claim 1, characterized in that: The following steps are involved: Step 1. Preparation of precursor solution: PbX2 and AX with a molar ratio of 1:1 were dissolved in DMF solvent to prepare an ABX3 perovskite precursor solution with a concentration of 0.5-1.5M; Step 2. Preparation of single crystal film: inject the above-mentioned precursor solution into the gap between two glass substrates with patterned ITO strip electrode arrays and an ITO spacing of 5-75 μm, form a confined space through a 10-100 μm thickness control spacer, and thermally anneal at 60-100°C for 48-168 hours to obtain a single crystal film; Step 3. Electrode integration: Use electron beam evaporation process to deposit 30-100nm metal electrodes on the single crystal film, and bond the ITO electrode leads to the PCB substrate through gold wire ball bonding; Step 4. Packaging treatment: UV-curing epoxy resin is coated on the edge of the single crystal film to form a moisture-proof sealing structure.

5. The method for preparing a beam deflector based on the perovskite electro-optical effect according to claim 4, characterized in that: In the step 1: the ABX3 perovskite single crystal film is MAPbCl3, MAPbBr3, or MAPbI3.

6. The method for preparing a beam deflector based on the perovskite electro-optical effect according to claim 4, characterized in that: In the step 2: the thickness of the confined space is regulated by a polyimide gasket, with a tolerance of ≤±5 μm.

7. The method for preparing a beam deflector based on the perovskite electro-optical effect according to claim 4, characterized in that: In the step 3: the electrode is integrated into one of an electron beam evaporation process and a magnetron sputtering process, and the electrode material includes one of gold, silver, platinum, titanium, aluminum, copper, ITO, and IZO.

8. The method for preparing a beam deflector based on the perovskite electro-optical effect according to claim 4, characterized in that: The ITO electrode interval is 5-200 μm, and the number of leads is 2-16.

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