Broadband Near-Infrared Photodetector with 4-Amino-2,3,5,6-tetrafluorobenzoic Acid as Dopant and Preparation Method Thereof

Abstract

A broadband near-infrared photodetector doped with 4-amino-2,3,5,6-tetrafluorobenzoic acid and a preparation method thereof belong to the technical field of photoelectric detection. The detector is composed of an ITO anode, a PTAA hole transport layer, a FA 0.85 Cs 0.15 Pb 0.5 Sn 0.5 I3 perovskite active layer, a C 60 electron transport layer, a BCP hole blocking layer and a Cu cathode. The perovskite active layer doped with 4-amino-2,3,5,6-tetrafluorobenzoic acid can absorb light in the ultraviolet, visible and near-infrared bands, with a wavelength range from 300 to 1050 nm, having excellent light absorption coefficient, high carrier mobility and good carrier diffusion length, which can passivate the surface and grain boundary defects of perovskite, reduce the dark current and noise current of the device, improve the detection performance, and realize broadband near-infrared detection.

Description

Technical Field

[0001] The present invention belongs to the technical field of optoelectronic detection, and particularly relates to a broadband near-infrared photodetector based on organic-inorganic hybrid tin-lead perovskite doped with 4-amino-2,3,5,6-tetrafluorobenzoic acid and a preparation method thereof. The present invention applies organic-inorganic hybrid tin-lead mixed perovskite and uses 4-amino-2,3,5,6-tetrafluorobenzoic acid as a dopant, which contributes to broadening the light detection range of the perovskite photodetector, improving the detection sensitivity and reducing the noise. Background Art

[0002] A photodetector is a device that directly converts an optical signal into an electrical signal and can be widely applied in fields such as medical imaging, image sensing, optical communication, environmental monitoring, and military detection, and has important application values in both military and national economic fields. Perovskite materials have advantages such as a high light absorption coefficient, a high carrier mobility, a long exciton diffusion length, bipolar carrier transport ability, and an adjustable bandgap, and are favored by researchers in the field of optoelectronic detection. General lead-based perovskites exhibit high absorption ability in the visible light region, but cannot absorb light in a wider wavelength band, which limits the application of infrared band detection. How to fabricate a perovskite photodetector that can detect light in a wider wavelength band while maintaining a high detection rate has become an important issue in the field. Some researchers have found that tin-lead mixed perovskite can well solve this problem, and the detection range of a photodetector based on tin-lead perovskite can reach 1050 nm and shows a high spectral response in the near infrared.

[0003] However, tin-based perovskite has a problem that cannot be ignored. Stannous tin is easily oxidized to stannic tin, which will generate many vacancies in the perovskite, leading to the generation of defects, and the defects will greatly reduce the performance of the photodetector. Therefore, relevant research must fabricate a detector with a high detection rate, low noise, and a wide wavelength band. Summary of the Invention

[0004] The purpose of the present invention is to provide a broadband near-infrared photodetector based on organic-inorganic hybrid tin-lead mixed perovskite doped with 4-Amino-2,3,5,6-tetrafluorobenzoic Acid (4-amino-2,3,5,6-tetrafluorobenzoic acid, with the molecular formula C 7 H 3 F 4 NO 2 , and a molecular weight of 209.0978) material and a preparation method thereof by using a simple process.

[0005] The molecular formula of 4-amino-2,3,5,6-tetrafluorobenzoic acid is as follows:

[0006]

[0007] Among them, the fluorinated group has certain hydrophobicity, while the amino group and carboxyl group can passivate uncoordinated lead and tin ions. For the first time, 4-amino-2,3,5,6-tetrafluorobenzoic acid is applied to the field of photodetectors in the present invention.

[0008] The device structure of the tin-lead perovskite photodetector from bottom to top is successively: ITO anode, PTAA hole transport layer, FA doped with 4-amino-2,3,5,6-tetrafluorobenzoic acid 0.85 Cs 0.15 Pb 0.5 Sn 0.5 I 3 perovskite active layer, C 60 electron transport layer, BCP hole blocking layer and Cu cathode. The FA doped with 4-amino-2,3,5,6-tetrafluorobenzoic acid in the photodetector 0.85 Cs 0.15 Pb 0.5 Sn 0.5 I 3 perovskite active layer can absorb light in the ultraviolet, visible and near-infrared bands, with a wavelength range from 300 to 1050 nm, realizing broadband near-infrared detection. Doping a certain amount of 4-amino-2,3,5,6-tetrafluorobenzoic acid in the perovskite can passivate the surface and grain boundary defects of the perovskite, mainly by binding to uncoordinated lead and tin ions, thereby reducing the dark current and noise current of the device and improving the detection performance.

[0009] In this device structure, PTAA is poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], C 60 is fullerene, BCP is 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline, and the perovskite active layer is made by mixing FAI (formamidinium iodide), CsI (cesium iodide), PbI 2 (lead iodide), SnI 2 (stannous iodide) and the additive SnF 2 (stannous fluoride), which has excellent light absorption coefficient, high carrier mobility and good carrier diffusion length. The materials and organic solvents used in the present invention can be obtained by purchase.

[0010] A preparation method of a broadband near-infrared photodetector using 4-amino-2,3,5,6-tetrafluorobenzoic acid as a dopant is as follows:

[0011] 1) Substrate treatment

[0012] The ITO conductive glass is successively ultrasonically treated with isopropanol, absolute ethanol, and deionized water for 15 - 30 minutes each, and then dried for standby under nitrogen treatment;

[0013] 2) Preparation of the hole transport layer and the perovskite active light-absorbing layer

[0014] (1) Solution preparation

[0015] ① Dissolve PTAA in toluene solvent to prepare a solution with a concentration of 1.0 - 3.0 mg / mL, and stir at room temperature on a magnetic stirring table for 6 - 8 hours to fully dissolve and obtain the PTAA solution;

[0016] ② Dissolve FAI, CsI, PbI 2 , SnI 2 and SnF 2 in a mixed solvent of DMF (N,N-dimethylformamide) and DMSO (dimethyl sulfoxide) with a volume ratio of 4 - 9:1 in a molar ratio of 0.85:0.15:0.5:0.5:0.05 to prepare a solution with a concentration of 1.0 - 2.0 mol / L; then add 4-amino-2,3,5,6-tetrafluorobenzoic acid with a molar ratio of 0.01 - 0.2:1 to SnI 2 and stir on a hot stage at 60 - 80 °C for 6 - 8 hours to fully dissolve. The stirring process is carried out in a nitrogen environment to obtain a perovskite precursor solution doped with 4-amino-2,3,5,6-tetrafluorobenzoic acid;

[0017] (2) Preparation of the hole transport layer and the perovskite active layer

[0018] ① Treat the cleaned ITO conductive glass in an ultraviolet cleaning machine for 10 - 30 minutes, and then spin-coat the PTAA solution on the ITO glass in a nitrogen environment at a spin-coating speed of 3000 - 5000 rpm for 30 - 50 seconds, and then place it on a hot stage at 90 - 105 °C for annealing for 15 - 30 minutes to prepare a PTAA hole transport layer on the ITO conductive glass with a thickness of 1 - 5 nm;

[0019] ② Spin-coat the perovskite precursor solution doped with 4-amino-2,3,5,6-tetrafluorobenzoic acid onto the PTAA hole transport layer at a speed of 3000 - 5000 rpm for 30 - 60 seconds. During the last 10 - 15 seconds before the spin-coating ends, add 150 - 300 μL of antisolvent such as toluene, chlorobenzene or ether. After the spin-coating process, anneal it on a hot plate at 100 - 120 °C for 15 - 30 minutes to obtain a perovskite active layer doped with 4-amino-2,3,5,6-tetrafluorobenzoic acid on the PTAA hole transport layer, with a thickness of 400 - 800 nm;

[0020] 3) Preparation of electron transport layer, hole blocking layer and metal electrode

[0021] ① Under a vacuum condition of 1×10 -4 ~5×10 -4 Pa, evaporate a layer of C 60 material with a thickness of 10 - 30 nm and an evaporation rate of 0.01 - 0.03 nm / s on the perovskite active layer doped with 4-amino-2,3,5,6-tetrafluorobenzoic acid to obtain the electron transport layer;

[0022] ② Evaporate a layer of BCP material with a thickness of 7 - 10 nm and an evaporation rate of 0.01 - 0.03 nm / s on the C 60 electron transport layer to obtain the hole blocking layer;

[0023] ③ Evaporate a layer of Cu material with a thickness of 80 - 100 nm and an evaporation rate of 0.1 - 0.15 nm / s on the BCP hole blocking layer to obtain the metal electrode; Thus, a broadband near-infrared photodetector based on organic-inorganic hybrid tin-lead perovskite doped with 4-amino-2,3,5,6-tetrafluorobenzoic acid as described in the present invention is prepared. Description of the Drawings

[0024] Figure 1 : Schematic structural diagram of a broadband near-infrared photodetector based on organic-inorganic hybrid tin-lead perovskite doped with 4-amino-2,3,5,6-tetrafluorobenzoic acid as described in the present invention; The names of each part are: ITO conductive glass 1, PTAA hole transport layer 2, FA 0.85 Cs 0.15 Pb 0.5 Sn 0.5 I 3 perovskite active layer 3, C60 electron transport layer 4, BCP hole blocking layer 5, Cu metal electrode 6.

[0025] Figure 2: Current density-voltage (J-V) characteristic curves of the pure perovskite device A prepared in Example 1 and the perovskite device B doped with 4-amino-2,3,5,6-tetrafluorobenzoic acid prepared in Example 2; voltage scanning range: -0.5 to 1.3 V.

[0026] Curve a represents the dark current (in the dark condition) curve of the pure perovskite device prepared in Example 1;

[0027] Curve b represents the photocurrent (AM 1.5G standard solar illumination) curve of the pure perovskite device prepared in Example 1;

[0028] Curve c represents the dark current (in the dark condition) curve of the perovskite device doped with 4-amino-2,3,5,6-tetrafluorobenzoic acid prepared in Example 2;

[0029] Curve d represents the photocurrent (AM 1.5G standard solar illumination) curve of the perovskite device doped with 4-amino-2,3,5,6-tetrafluorobenzoic acid prepared in Example 2;

[0030] It can be seen that for the perovskite device B doped with 4-amino-2,3,5,6-tetrafluorobenzoic acid, while maintaining the original photocurrent level, the dark current density is greatly reduced, which endows the photodetector with excellent detection performance.

[0031] Figure 3 : External quantum efficiency (EQE) spectrograms of the pure perovskite photodetectors A and the perovskite devices B doped with 4-amino-2,3,5,6-tetrafluorobenzoic acid prepared in Example 1 and Example 2.

[0032] As shown in the figure, both devices can detect light in the ultra-wide wavelength band of 300 - 1050 nm, and the device doped with 4-amino-2,3,5,6-tetrafluorobenzoic acid shows a stronger spectral response, especially in the near-infrared band, indicating that the defects at the band edge are effectively passivated by the dopant, which is of great significance for the practical application of the detector.

[0033] Figure 4 : Responsivity (R) curve graphs of the pure perovskite photodetectors A and the perovskite devices B doped with 4-amino-2,3,5,6-tetrafluorobenzoic acid prepared in Example 1 and Example 2 at different wavelengths.

[0034] By comparing the responsivity curves, it can be seen that the perovskite photodetector doped with 4-amino-2,3,5,6-tetrafluorobenzoic acid shows a higher optical response than the pure perovskite device in the entire response range. After calculation, the highest responsivity reaches 0.52 A / W in the near-infrared band at 855 nm, which reflects the excellent spectral response of the doped photodetector to near-infrared light.

[0035] Figure 5: Specific detectivity (D) of the pure perovskite device A prepared in Example 1 and Example 2 and the perovskite device B doped with 4-amino-2,3,5,6-tetrafluorobenzoic acid at different wavelengths * ) curve graph.

[0036] Detection sensitivity is an important indicator reflecting the detection ability of a photodetector. The perovskite photodetector doped with 4-amino-2,3,5,6-tetrafluorobenzoic acid exhibits a specific detectivity exceeding 1×10 11 Jones (cm Hz 1 / 2 W -1 ) in the wavelength range of 350 - 965 nm, and shows a maximum specific detectivity of 2.87×10 11 Jones (cm Hz 1 / 2 W -1 ) at the near-infrared band of 855 nm, which is much higher than the specific detectivity of the pure perovskite device at the same wavelength (3.49×10 10 Jones), being about one order of magnitude higher. Compared with the undoped device, the photodetector doped with 4-amino-2,3,5,6-tetrafluorobenzoic acid shows a higher specific detectivity, creating more possibilities for practical applications. It can be clearly seen from the figure that the perovskite photodetector doped with 4-amino-2,3,5,6-tetrafluorobenzoic acid prepared in the present invention can effectively improve the detection performance of the device.

[0037] Figure 6 : Comparison graph of the noise current of the pure perovskite photodetector A and the perovskite device B doped with 4-amino-2,3,5,6-tetrafluorobenzoic acid prepared in Example 1 and Example 2 at different frequencies.

[0038] From the data in the figure, the noise current of the pure perovskite photodetector at 70 Hz is 2.62×10 -12 A Hz -1 , while the noise current of the device doped with 4-amino-2,3,5,6-tetrafluorobenzoic acid is one order of magnitude lower than that of the undoped device (at 70 Hz, 3.79×10 -13 A Hz -1 ), and shows an almost frequency-independent characteristic, which benefits from the passivation effect of 4-amino-2,3,5,6-tetrafluorobenzoic acid on perovskite defects. Specific implementation mode

[0039] Example 1:

[0040] 1. Ultrasonically clean the ITO conductive glass: Treat it with isopropyl alcohol, ethanol, and deionized water in sequence for 15 minutes, then dry the ITO conductive glass with a nitrogen stream and perform ultraviolet ozone treatment for 10 minutes;

[0041] 2. Dissolve PTAA in toluene at a concentration of 2 mg / mL, stir for 6 hours at room temperature. After complete dissolution, spin-coat it on the ITO conductive glass at a speed of 4000 rpm for 30 seconds, and then dry it on a hot plate at 90 °C for 20 minutes to obtain the PTAA hole transport layer;

[0042] 3. Mix FAI, CsI, PbI 2 、SnI 2 and SnF 2 in a molar ratio of 0.85:0.15:0.5:0.5:0.05 and dissolve them in a mixed solvent of DMF and DMSO (volume ratio 4:1) to prepare a solution with a concentration of 1.2 mol / L. Stir on a hot plate at 60 °C for 6 hours to obtain the perovskite precursor solution; The stirring process is carried out in a nitrogen environment;

[0043] Then spin-coat the perovskite precursor solution on the PTAA hole transport layer at a speed of 4500 rpm for 40 s, and drop 200 μL of diethyl ether as an anti-solvent 12 s before the end of the spin-coating process; Subsequently, anneal it on a hot plate at 105 °C for 25 minutes to obtain the perovskite active layer;

[0044] 4. Transfer the ITO conductive glass with the prepared perovskite active layer to a multi-source organic vapor phase molecular deposition system. Wait for the vacuum to drop below 8×10 -4 Pa, and grow a layer of C 60 material with a thickness of 20 nm and an evaporation rate of 0.02 nm / s as the electron transport layer by thermal evaporation; Then evaporate a 7-nm BCP material with an evaporation rate of 0.02 nm / s as the hole blocking layer;

[0045] 5. Finally, evaporate an 85-nm Cu as the metal electrode with an evaporation rate of 0.1 nm / s and a vacuum below 1×10 -3 Pa. Thus, the photodetector based on organic-inorganic hybrid tin-lead perovskite of the present invention is prepared as the basic device A.

[0046] Example 2:

[0047] 1. Ultrasonically clean the ITO conductive glass, treat it with isopropyl alcohol, ethanol, and deionized water in sequence for 15 minutes, then dry the ITO conductive glass with a nitrogen stream and perform ultraviolet ozone treatment for 10 minutes;

[0048] 2. Dissolve PTAA in toluene at a concentration of 2 mg / mL, stir for 6 hours at room temperature. After complete dissolution, spin-coat it on ITO conductive glass at a speed of 4000 rpm for 30 seconds, and then dry it on a hot plate at 90 °C for 20 minutes to obtain the PTAA hole transport layer;

[0049] 3. Mix FAI, CsI, PbI 2 , SnI 2 and SnF 2 in a molar ratio of 0.85:0.15:0.5:0.5:0.05 and dissolve them in a mixed solvent of DMF and DMSO (volume ratio 4:1) to prepare a solution with a concentration of 1.2 mol / L. And add 4-amino-2,3,5,6-tetrafluorobenzoic acid material with a molar ratio of 0.05:1 to SnI 2 . Stir on a hot plate at 60 °C for 6 hours to obtain a perovskite precursor solution doped with 4-amino-2,3,5,6-tetrafluorobenzoic acid; the stirring process is carried out in a nitrogen environment; then spin-coat the perovskite precursor solution doped with 4-amino-2,3,5,6-tetrafluorobenzoic acid on the PTAA hole transport layer at a spin-coating speed of 4500 rpm for 40 s, and drop 200 μL of diethyl ether as an anti-solvent 12 s before the end of the spin-coating program; then anneal it on a hot plate at 105 °C for 25 minutes to obtain a perovskite active layer doped with 4-amino-2,3,5,6-tetrafluorobenzoic acid;

[0050] 4. Transfer the ITO conductive glass with the prepared perovskite active layer doped with 4-amino-2,3,5,6-tetrafluorobenzoic acid to a multi-source organic vapor phase molecular deposition system. Wait for the vacuum degree to drop below 8×10 -4 Pa, and grow a layer of C 60 material with a thickness of 20 nm and an evaporation rate of 0.02 nm / s by thermal evaporation as the electron transport layer; then evaporate a 7-nm BCP material with an evaporation rate of 0.02 nm / s as the hole blocking layer;

[0051] 5. Finally, evaporate an 85-nm Cu as the metal electrode with an evaporation rate of 0.1 nm / s and a vacuum degree lower than 1×10 -3 Pa. Thus, the photodetector based on organic-inorganic hybrid tin-lead perovskite doped with 4-amino-2,3,5,6-tetrafluorobenzoic acid described in the present invention is prepared as the optimized device B.

Claims

1. A method for preparing a broadband near-infrared photodetector using 4-amino-2,3,5,6-tetrafluorobenzoic acid as a dopant, the steps are as follows: 1) Substrate treatment The ITO conductive glass is ultrasonically treated with isopropyl alcohol, absolute ethanol, and deionized water for 15 - 30 minutes in sequence, and then dried for standby under nitrogen treatment; 2) Preparation of hole transport layer and perovskite active light-absorbing layer (1) Solution preparation ① Dissolve PTAA in toluene solvent to form a solution with a concentration of 1.0 - 3.0 mg / mL, and stir at room temperature on a magnetic stirrer for 6 - 8 hours to fully dissolve to obtain PTAA solution; ②Dissolve FAI, CsI, PbI 2 , SnI 2 , and SnF 2 in a mixed solvent of DMF and DMSO with a volume ratio of 4 - 9:1 at a molar ratio of 0.85:0.15:0.5:0.5:0.05 to prepare a solution with a concentration of 1.0 - 2.0 mol / L; then add 4-amino-2,3,5,6-tetrafluorobenzoic acid with a molar ratio of 0.01 - 0.2:1 to SnI 2 ​ Among them, Then stir on a hot plate at 60 - 80 °C for 6 - 8 hours, and the stirring process is carried out in a nitrogen environment to obtain a perovskite precursor solution doped with 4-amino-2,3,5,6-tetrafluorobenzoic acid; (2) Preparation of hole transport layer and perovskite active layer ① Treat the cleaned ITO conductive glass in an ultraviolet cleaning machine for 10 - 30 minutes, then spin-coat the PTAA solution on the ITO glass in a nitrogen environment at a spin-coating speed of 3000 - 5000 rpm for 30 - 50 seconds, and then place it on a hot plate at 90 - 105 °C for annealing for 15 - 30 minutes, thereby preparing a PTAA hole transport layer on the ITO conductive glass with a thickness of 1 - 5 nm; ② Spin-coat the perovskite precursor solution doped with 4-amino-2,3,5,6-tetrafluorobenzoic acid onto the PTAA hole transport layer at a speed of 3000 - 5000 rpm for 30 - 60 seconds, and add 150 - 300 μL of toluene, chlorobenzene, or ether antisolvent within 10 - 15 seconds before the end of spin-coating; after the spin-coating process, anneal on a hot plate at 100 - 120 °C for 15 - 30 minutes, thereby obtaining a perovskite active layer doped with 4-amino-2,3,5,6-tetrafluorobenzoic acid on the PTAA hole transport layer with a thickness of 400 - 800 nm; 3) Preparation of electron transport layer, hole blocking layer, and metal electrode ① Under a vacuum condition of 1×10 -4 ~5×10 -4 Pa, a layer of C 60 material with a thickness of 10 - 30 nm and an evaporation rate of 0.01 - 0.03 nm / s is vapor-deposited on a perovskite active layer doped with 4-amino-2,3,5,6-tetrafluorobenzoic acid to obtain an electron transport layer; ② On C 60 Deposit a layer of BCP material on the electron transport layer with a thickness of 7 - 10 nm and an evaporation rate of 0.01 - 0.03 nm / s to obtain a hole blocking layer; ③ Evaporate a layer of Cu material on the BCP hole blocking layer with a thickness of 80 - 100 nm and an evaporation rate of 0.1 - 0.15 nm / s to obtain a metal electrode; thus, a broadband near-infrared photodetector based on organic-inorganic hybrid tin-lead perovskite using 4-amino-2,3,5,6-tetrafluorobenzoic acid as a dopant described in the present invention is prepared; Among them, PTAA is poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], BCP is 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline, FAI is formamidinium iodide, and the structural formula of 4-amino-2,3,5,6-tetrafluorobenzoic acid is as shown below, 2. A broadband near-infrared photodetector using 4-amino-2,3,5,6-tetrafluorobenzoic acid as a dopant, Characterized in that: It is prepared by the method described in claim 1.

Images