Dual-response-mode organic photoelectric detector and preparation method thereof

Abstract

The invention discloses a photovoltaic / photomultiplier dual-response-mode organic photoelectric detector and a preparation method thereof, and the dual-response-mode organic photoelectric detector comprises a substrate, an anode layer, a hole transport layer, a photoelectric regulation and control layer, an active layer, an electron transport layer and a cathode layer which are sequentially arranged from bottom to top. The material of the photoelectric regulation and control layer is Cs3Cu2I5 nanocrystalline; the active layer includes a polymer donor layer and an organic acceptor layer. The active layer is of a quasi-double-layer structure mainly comprising a polymer, a Cs3Cu2I5 nanocrystalline layer is introduced in front of the active layer to serve as the photoelectric regulation and control layer, electron traps in the photoelectric regulation and control layer are used for assisting a large number of tunneling injection functions of external circuit holes, and a photomultiplication mode under low positive bias voltage and a photovoltaic detection mode under zero / reverse bias voltage are achieved; and the flexible detection of strong / weak light of the photoelectric detector in a complex environment can be met.

Description

Technical Field

[0001] The present invention relates to the technical field of photoelectric detection, and in particular to a dual-response mode organic photoelectric detector and a preparation method thereof. Background Art

[0002] Photodetectors are electronic devices that can convert optical signals into electrical signals and are an important part of optoelectronic systems. Thanks to the advantages of organic materials such as adjustable spectral response range, large-area preparation by solution method, compatibility with various substrates and low preparation cost, organic photodetectors have shown good application prospects in the field of photodetection. Traditional diode-type organic photodetectors usually work in photovoltaic mode, that is, the photocurrent obtained by the device is composed of photogenerated carriers collected by the electrodes at both ends. Its defects are: low photogenerated current, which is not conducive to weak light detection. Different from the photovoltaic detection mode, the working principle of photomultiplier organic photodetectors is based on the large-scale tunneling injection of single charges in the external circuit induced by carrier traps, so it has a very high output current, which is conducive to weak light signal detection. However, photomultiplier detectors usually require extremely high bias operating voltages, and when the intensity of the light signal increases, the problems of anti-breakthrough and heat dissipation caused by high power consumption cannot be ignored, so photomultiplier photodetectors cannot detect strong light signals. It can be seen that the single detection mode greatly limits the application of organic optoelectronic detectors. Therefore, how to realize photovoltaic and photomultiplier dual-mode operation in organic photodetectors has become an important research direction. Summary of the invention

[0003] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a dual-response mode organic photodetector and a preparation method thereof, so as to solve the technical problem that the purple phosphorus material in the prior art is unstable in the air.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions to achieve the above problems:

[0005] A dual-response mode organic photodetector comprises a substrate, an ITO anode layer, a hole transport layer, a photoelectric regulation layer, an active layer, an electron transport layer and a cathode layer arranged in sequence from bottom to top; the material of the photoelectric regulation layer is Cs3Cu2I5 nanocrystal; the active layer comprises a donor layer and an acceptor layer.

[0006] The present invention also has the following technical features:

[0007] Specifically, the substrate is a rigid substrate or a flexible substrate. The rigid substrate includes glass or quartz; the flexible substrate includes polyvinyl alcohol, polyester, polyimide and polyethylene naphthalate.

[0008] Furthermore, the material of the hole transport layer is PEDOT:PSS, the material of the electron transport layer is PDINO; and the material of the cathode layer is selected from one of Au, Al, Pt and Ag.

[0009] Furthermore, the material of the organic donor layer is selected from one of PCDTBT, PM6, D18 and their derivatives, and the material of the acceptor layer is selected from one of PCBM and its derivatives, Y6 and its derivatives, L8BO and its derivatives, and a mixture of polymer N2200 and L8BO, wherein the mass ratio of N2200 to L8BO in the mixture of polymer N2200 and L8BO is 7:3.

[0010] Furthermore, the thickness of the donor layer is 68 to 72 nm, the thickness of the acceptor layer is 48 to 52 nm, the thickness of the hole transport layer is 16 to 22 nm, the thickness of the photoelectric regulation layer is 20 to 24 nm, and the thickness of the cathode layer is 80 to 120 nm.

[0011] The present invention also protects a method for preparing a dual-response mode organic photodetector, comprising the following steps:

[0012] Step 1, forming an ITO anode layer on one side of the substrate;

[0013] Step 2, ultrasonically cleaning the surface of the ITO anode layer;

[0014] Step 3, spin coating the PEDOT:PSS solution on the ITO anode layer to form a hole transport layer;

[0015] Step 4, spin coating the Cs3Cu2I5 nanocrystal solution on the hole transport layer to form a photoelectric control layer;

[0016] Step 5, spin-coating a donor solution on the upper surface of the photoelectric regulation layer to obtain a donor layer; spin-coating an acceptor solution on the upper surface of the donor layer to obtain an acceptor layer, wherein the donor layer and the acceptor layer form an active layer;

[0017] Step 6, spin coating an electron transport layer precursor solution on the active layer to form an electron transport layer;

[0018] Step 7: evaporate a cathode layer on the electron transport layer to obtain a photodetector with photovoltaic and photomultiplier response modes.

[0019] Furthermore, the donor solution includes the material of the donor layer and a halogen solvent, and the halogen solvent includes chloroform and chlorobenzene; the concentration of the donor solution is 8-12 mg / mL.

[0020] Furthermore, the receptor solution includes receptor layer materials and a solvent, the solvent includes chloroform, chlorobenzene and toluene, and the concentration of the receptor solution is 6-10 mg / mL.

[0021] Furthermore, the Cs3Cu2I5 nanocrystal solution includes Cs3Cu2I5 nanocrystals and a halogen solvent, the halogen solvent is chloroform, and the concentration of the Cs3Cu2I5 nanocrystal solution is 1 to 4 mg / mL.

[0022] Furthermore, the electron transport layer precursor solution includes PDINO and a solvent, the solvent is methanol, and the concentration of the electron transport layer precursor solution is 2 mg / mL.

[0023] Compared with the prior art, the present invention has the following technical effects:

[0024] (1) The active layer of the photodetector provided by the present invention adopts a quasi-double-layer structure mainly composed of polymers, and a Cs3Cu2I5 nanocrystalline layer is introduced in front of the active layer as a photoelectric control layer. The self-trapped electron traps in the photoelectric control layer are used to assist the large-scale tunneling injection of holes in the external circuit, thereby realizing a photomultiplier mode under low positive bias voltage and a photovoltaic detection mode under zero / reverse bias voltage.

[0025] (2) Compared with organic photodetectors with only a single working mode, the present invention has the characteristics of simple structure, low cost, high bearing capacity, high reliability, and easy maintenance, and can meet the needs of flexible detection of strong / weak light by photodetectors in complex environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the structure of the photoelectric detector of the present invention.

[0027] Figure 2 The external quantum efficiency curves of the photodetector of Example 1 under forward and reverse bias with and without the photoelectric regulation layer;

[0028] Figure 3 The dark state and light state current density-voltage characteristic curves of the photodetector of Example 1;

[0029] Figure 4 is the external quantum efficiency curve of the photodetector of Example 1;

[0030] Figure 5 is the responsivity curve of the photodetector of Example 1;

[0031] Figure 6 This is the relative detection rate curve of the photodetector of Example 1.

[0032] The meaning of each symbol in the accompanying drawings:

[0033] 1- anode layer, 2- hole transport layer, 3- photoelectric regulation layer, 4- donor layer, 5- acceptor layer, 6- electron transport layer, 7- cathode layer.

[0034] The specific contents of the present invention are further explained in detail below in conjunction with embodiments. DETAILED DESCRIPTION

[0035] Specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent changes made on the basis of the technical solution of this application fall within the protection scope of the present invention.

[0036] The terms "upper", "lower", "front", "rear", "top", "bottom" and the like used in the present invention to indicate directions or positional relationships are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific direction, be constructed and operate in a specific direction. "Inside" and "outside" refer to the inside and outside of the contours of the corresponding components, and the above terms should not be understood as limiting the present invention.

[0037] All raw materials in the present invention are commercially available unless otherwise specified. They include: PM6: solid powder, molecular weight 50,000; N2200: solid powder, molecular weight 20,000; L8BO: solid powder, purity 99.99%; PEDOT:PSS: liquid, solid content 1.0-1.3%, mass ratio of PEDOT to PSS 1:2.5, resistance 500-5000Ω / cm; PDINO: solid powder, purity 99.99%; Cs2CO3: solid powder, purity 98%; CuI : solid powder, purity 99.99%; deionized water: liquid liquid, purity 99.99%; oleylamine: liquid liquid, purity 90%; octadecene: liquid liquid, purity 90%; oleic acid: liquid liquid, purity 90%; deionized water: liquid liquid, purity 99.99%; acetone: liquid liquid, purity 99.5%; ethanol, isopropanol, chloroform, chlorobenzene, methanol: liquid liquid, purity 99.99%; aluminum: solid particles, φ6*6mm, purity 99.99%. Indium tin oxide ITO: solid solid.

[0038] The detection instruments used in the present invention include: a solar simulator (Newport model 94021A); a Keithley 2400 digital source meter to obtain the current density-voltage curve, and a commercial quantum efficiency tester (QE-R3018, Enli Technology Co., Ltd.) to measure the external quantum efficiency EQE of the photodetector.

[0039] Example 1

[0040] Following the above technical solution, Figure 1 As shown, this embodiment provides a dual-response mode organic photodetector, which includes, from bottom to top, a substrate, an anode layer 1, a hole transport layer 2, a photoelectric control layer 3, a donor layer 4, an acceptor layer 5, an electron transport layer 6 and a cathode layer 7, wherein the donor layer 4 and the acceptor layer 5 constitute an active layer. In this embodiment, the polymer donor layer and the organic acceptor layer are two independent layers, and the light can be absorbed and transmitted by the polymer donor layer and the organic acceptor layer respectively, without confusion of absorption and transmission of light. By adjusting the ratio of the donor and the acceptor, the band structure can be adjusted to achieve charge transfer.

[0041] By applying different bias voltages, the two different detection modes of the photodetector can be controlled, while maintaining high external quantum efficiency EQE, response rate R and specific detection rate D.

[0042] As a solution of this embodiment, the substrate is glass.

[0043] As a scheme of this embodiment, the material of the anode layer is indium tin oxide; the material of the hole transport layer is PEDOT:PSS; the material of the donor layer is PM6, and the material of the acceptor layer is N2200:L8BO; the material of the electron transport layer is PDINO; and the material of the cathode layer is aluminum.

[0044] As a scheme of this embodiment, the thickness of the hole transport layer is 16-22nm, the thickness of the photoelectric control layer is 20-24nm, the thickness of the donor layer is 68-72nm, the thickness of the acceptor layer is 48-52nm, and the thickness of the cathode layer is 80-120nm.

[0045] Example 2

[0046] This embodiment discloses a method for preparing a dual-response mode organic photodetector provided in Embodiment 1, comprising the following steps:

[0047] Step 1: Form an ITO anode layer on one side of the substrate, with a transmittance of about 86%, a surface roughness Ra of 0.16-0.32nm, and a square resistance of 10Ω / cm 2 ;

[0048] Step 2, ultrasonically cleaning the surface of the ITO anode layer;

[0049] Ultrasonic cleaning is performed in the following order:

[0050] (1) placing an ITO conductive glass sheet (i.e., glass having an ITO anode layer on the surface) in an ultrasonic cleaner, adding deionized water, and ultrasonically cleaning for 15 minutes;

[0051] (2) Place the ITO conductive glass sheet in an ultrasonic cleaner, add acetone, and perform ultrasonic cleaning for 15 minutes;

[0052] (3) Place the ITO conductive glass sheet in an ultrasonic cleaner, add acetone, and perform ultrasonic cleaning for 15 minutes;

[0053] (4) The washed ITO conductive glass sheet was treated with UV-ozone cleaning for 15 minutes.

[0054] Step 3, spin coating the PEDOT:PSS solution on the ITO anode layer to form a hole transport layer;

[0055] The PEDOT:PSS solution was obtained by uniformly mixing 1 ml of pure PEDOT:PSS solution with 1 ml of deionized water; 50 μL was dropped on the surface of the ITO anode layer and spin coated at 4000 rpm for 40 seconds; then annealed at 150° C. for 15 minutes and allowed to stand at room temperature for at least 10 minutes to obtain a hole transport layer.

[0056] Step 4, spin coating the Cs3Cu2I5 nanocrystal solution on the hole transport layer to form a photoelectric control layer;

[0057] Specifically, it includes: dissolving 2 mg of Cs3Cu2I5 nanocrystal solid in 1 ml of chloroform solution to obtain a Cs3Cu2I5 solution with a concentration of 2 mg / mL; taking 40 μL and dropping it on the surface of the hole transport layer, and spin coating it at a speed of 2000 rpm for 40 seconds; annealing at 100°C for 10 minutes, and then for more than 10 minutes to obtain the photoelectric control layer.

[0058] Step 5, spin-coating a donor solution on the upper surface of the photoelectric regulation layer to obtain a donor layer; spin-coating an acceptor solution on the upper surface of the donor layer to obtain an acceptor layer, wherein the donor layer and the acceptor layer form an active layer;

[0059] Specifically, the process includes: dissolving 10 mg of PM6 in 1 ml of chloroform solution to obtain a PM6 solution with a concentration of 10 mg / mL; dissolving 5.6 mg of N2200 and 2.4 mg of L8BO in 1 ml of chlorobenzene solution to obtain a N2200:L8BO mixed solution with a mass ratio of 7:3 and a concentration of 8 mg / mL; dropping 30 μL of the PM6 solution on the upper surface of the photoelectric regulation layer, and spin coating at a speed of 1500 rpm for 30 seconds to obtain a PM6 donor layer; after standing in a glove box for 5 minutes, dropping 40 μL of the N2200:L8BO mixed solution on the upper surface of the PM6 donor layer, and spin coating at a speed of 1500 rpm for 30 seconds to obtain an acceptor layer. The donor layer and the acceptor layer constitute an active layer.

[0060] Step 6, spin coating an electron transport layer precursor solution on the active layer to form an electron transport layer;

[0061] Specifically, the process includes: dissolving 2 mg of PDINO in 1 ml of methanol solution to obtain a PDINO solution with a concentration of 2 mg / mL; dropping 50 μL of the PDINO solution on the upper surface of the acceptor layer, and spin coating at a rotation speed of 2000 rpm for 40 seconds; and obtaining an electron transport layer.

[0062] Step 7: evaporate a cathode layer on the electron transport layer to obtain a photodetector with photovoltaic and photomultiplier response modes.

[0063] The evaporation is carried out in a vacuum evaporation furnace, the component to be processed is placed on the turntable on the top of the furnace chamber, and the substrate of the electron transport layer faces downward; the evaporation material particles of the formula amount are placed in a tungsten boat; the vacuum degree in the furnace is ≤0.0004Pa, and the turntable speed is 5r / min; during the evaporation process, the growth rate of the cathode layer is set to 3nm / s, and the thickness of the cathode layer is 100±20nm.

[0064] The performance of the photoelectric detector prepared in this embodiment was tested, analyzed and characterized, and the results are as follows: Figure 2 It can be seen from the external quantum efficiency characteristic curve that compared with the control device, the organic photodetector with the photoelectric regulation layer inserted has an obvious photomultiplier effect with an external quantum efficiency greater than 100% under positive bias, and the external quantum efficiency is still greater than the control device at zero bias. Therefore, after inserting the photoelectric regulation layer composed of the Cs3Cu2I5 nanocrystalline layer, the photodetector realizes the transition from a single photovoltaic working mode to a photovoltaic / photomultiplier dual mode. The reason is that under forward bias, more photogenerated electrons are captured in the electron traps of the photoelectric regulation layer, resulting in the enhancement of the energy band of the photoelectric regulation layer, realizing the photomultiplier effect, and the photodetector is in the photomultiplier working mode; under reverse bias and zero bias, the photogenerated excitons dissociate at the donor-acceptor interface to form a photogenerated current, and the photodetector is in the photovoltaic working mode.

[0065] Depend on Figure 3 It can be seen from the bright state and dark state current density-voltage characteristic curves that the photodetector provided in this embodiment has an obvious bright-dark current ratio under forward and reverse bias, ensuring the detection performance of the photodetector.

[0066] In addition, this embodiment also analyzes the detection performance of a single mode of the photodetector under forward and reverse bias, that is, the external quantum efficiency EQE, responsivity R and specific detection rate D* performance that vary with wavelength. The results are as follows Figures 4 to 6 shown.

[0067] It can be seen from the figure that the photodetector provided in this embodiment has high external quantum efficiency EQE, response rate R and specific detection rate D* in different working modes.

[0068] Specifically, at zero bias, the photodetector is in photovoltaic photodetection mode, at a wavelength of 620nm, the external quantum efficiency EQE is 57%, the response rate R is 0.3A / W, and the specific detection rate D* is 2x1010Jones. At a forward bias of 2V, the photodetector is in photomultiplier detection mode, at a wavelength of 780nm, the external quantum efficiency EQE is 127%, the response rate R is 0.8A / W, and the specific detection rate D* is 6x1010Jones. The photodetector has higher external quantum efficiency EQE and response rate R under forward bias mainly because: under forward bias, more photogenerated electrons are captured in the photoelectric regulation layer, resulting in the improvement of the energy band of the photoelectric regulation layer, which is conducive to the injection of holes from the external circuit, and improves the external quantum efficiency EQE and response rate R of the photodetector.

[0069] In summary, the photodetector provided by the present invention introduces a Cs3Cu2I5 nanocrystalline layer into the photodetector structure as a photoelectric control layer, which cleverly overcomes the shortcoming that the traditional organic photodetector has only a single working mode, realizes dual-mode photodetection under different bias voltages, and expands the application range of the device. And the active layer adopts a laminated polymer structure formed by a donor layer and an acceptor layer. The preparation method provided in this embodiment can accurately control the thickness of each layer, has good repeatability, is simple and convenient, and has low cost, and can obtain a high stability, external quantum efficiency EQE and response rate R dual response mode organic photodetector, which has potential application value.

[0070] What has been described above is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be conceived by a technician familiar with the field within the technical scope disclosed by the present invention without creative work are all covered by the protection scope of the present invention.

Claims

1. A dual-response mode organic photodetector, characterized in that: It includes a substrate, an anode layer, a hole transport layer, a photoelectric regulation layer, an active layer, an electron transport layer and a cathode layer arranged in sequence from bottom to top; the material of the photoelectric regulation layer is Cs3Cu2I5 nanocrystal; the active layer includes a polymer donor layer and an organic acceptor layer.

2. The dual-response mode organic photodetector according to claim 1, characterized in that: The substrate is a rigid substrate or a flexible substrate. The rigid substrate includes glass or quartz; the flexible substrate includes polyvinyl alcohol, polyester, polyimide and polyethylene naphthalate.

3. The dual-response mode organic photodetector according to claim 1, characterized in that: The material of the anode layer is indium tin oxide; the material of the hole transport layer is PEDOT:PSS; the material of the electron transport layer is PDINO; and the material of the cathode layer is selected from one of Au, Al, Pt and Ag.

4. The dual-response mode organic photodetector according to claim 1, characterized in that: The material of the organic donor layer is selected from one of PCDTBT, PM6, D18 and derivatives thereof, and the material of the acceptor layer is selected from one of PCBM and derivatives thereof, Y6 and derivatives thereof, L8BO and derivatives thereof, and a mixture of polymers N2200 and L8BO, wherein the mass ratio of N2200 to L8BO in the mixture of polymers N2200 and L8BO is 7:

3.

5. The dual-response mode organic photodetector according to claim 1, characterized in that: The thickness of the hole transport layer is 16-22 nm, the thickness of the photoelectric control layer is 20-24 nm, the thickness of the donor layer is 68-72 nm, the thickness of the acceptor layer is 48-52 nm, and the thickness of the cathode layer is 80-120 nm.

6. The method for preparing a dual-response mode organic photodetector according to any one of claims 1 to 5, characterized in that: The steps include: Step 1, forming an ITO anode layer on one side of the substrate; Step 2, ultrasonically cleaning the surface of the ITO anode layer; Step 3, spin coating the PEDOT:PSS solution on the ITO anode layer to form a hole transport layer; Step 4, spin coating the Cs3Cu2I5 nanocrystal solution on the hole transport layer to form a photoelectric control layer; Step 5, spin coating the donor solution on the upper surface of the photoelectric regulation layer to obtain a donor layer; Spin-coating an acceptor solution on the upper surface of the donor layer to obtain an acceptor layer, wherein the donor layer and the acceptor layer form an active layer; Step 6, spin coating an electron transport layer precursor solution on the active layer to form an electron transport layer; Step 7: evaporate a cathode layer on the electron transport layer to obtain a photodetector with photovoltaic and photomultiplier response modes.

7. The method for preparing a dual-response mode organic photodetector according to claim 6, characterized in that: The donor solution comprises the material of the donor layer and a halogen solvent, wherein the halogen solvent comprises chloroform and chlorobenzene; and the concentration of the donor solution is 8-12 mg / mL.

8. The method for preparing a dual-response mode organic photodetector according to claim 6, characterized in that: The receptor solution includes receptor layer materials and a solvent, wherein the solvent includes chloroform, chlorobenzene and toluene, and the concentration of the receptor solution is 6-10 mg / mL.

9. The method for preparing a dual-response mode organic photodetector according to claim 6, characterized in that: The Cs3Cu2I5 nanocrystal solution comprises Cs3Cu2I5 nanocrystals and a halogen solvent, wherein the halogen solvent is chloroform, and the concentration of the Cs3Cu2I5 nanocrystal solution is 1-4 mg / mL.

10. The method for preparing a dual-response mode organic photodetector according to claim 6, characterized in that: The electron transport layer precursor solution includes PDINO and a solvent, the solvent is methanol, and the concentration of the electron transport layer precursor solution is 2 mg / mL.

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