A high specific detectivity optical detection device and a preparation method thereof

Abstract

The application discloses a high specific detectivity optical detection device and a preparation method thereof. The detection device is composed of a bottom substrate, a conductive cathode, an electron transport layer, an organic photoactive layer, a hole transport layer and a metal anode. The photoactive layer adopts a polymer donor PDPP3T and a fullerene acceptor PC 71 BM is blended to form a bulk heterojunction, and a solvent additive 1,8-diiodooctane is added to regulate the heterojunction morphology. The electron transport layer uses pure zinc oxide as a single interface layer or ethoxylated polyethyleneimine modified zinc oxide as a composite interface. Under the action of a reasonable additive content, the dark current of the detection device is significantly reduced, and a low dark current and high specific detectivity optical detection device is realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of organic photodetector devices, and particularly relates to a high specific detectivity photodetector device and a preparation method thereof. BACKGROUND

[0002] In recent years, the development of organic semiconductor industry is rapid due to the rapid development of corresponding material and device technology. Compared with inorganic semiconductors, organic materials have the advantages of low processing cost, convenient solution processing, easy preparation of large-area devices, and light weight and flexible curling, which promotes organic photodetectors to gradually become the research focus of researchers in the field of photodetectors. At present, the performance of some organic photodetectors can reach or even exceed that of inorganic photodetectors, but the organic photodetectors also have their shortcomings.

[0003] Specific detectivity, as an important parameter of organic photodiode detectors, improving its value is the key to the development of organic photodiode detectors, and the dark current can be reduced and the specific detectivity can be improved through some device design and interface application.

[0004] In order to reduce the organic photodetector, many researchers have put forward their own ideas. Ma Dongge et al. introduced a cross-linked electron blocking layer poly-TPD, which reduced the dark current density, and the dark current density reached 0.64nA cm -2 at-0.5V bias, the EQE at 850nm wavelength was 27.7%, the response of the forward device to EQE was inhibited to a certain extent, and the specific detectivity was limited (Advanced Optical Materials 2015, 8, 311). Tedde et al. analyzed the influence of DIO on the performance of the device, but the use of spraying process did not significantly suppress the dark current, and the EQE response at long wavelength was not optimized (Organic Electronics 2017, 12, 54). The previous literature records that the research on the PDPP3T:PC 71 BM system photodetector adopts a forward structure, and the blocking layer used does not significantly suppress the dark current, resulting in low specific detectivity.

[0005] Therefore, it is of great research and invention significance to prepare a high specific detectivity photodetector device. SUMMARY

[0006] In order to solve the shortcomings and deficiencies of the prior art, the primary purpose of the present application is to provide a high specific detectivity photodetector device. The light active layer of the device is formed by blending a polymer donor PDPP3T and a fullerene acceptor PC 71 BM to form a bulk heterojunction, and a solvent additive 1,8-diiodooctane is added to regulate the morphology of the heterojunction, thereby improving the device performance.

[0007] Still another object of the present application is to provide a preparation method of the high specific detectivity optical detection device.

[0008] The object of the present application is achieved by the following technical solutions.

[0009] A high specific detectivity optical detection device, which has a flip-chip structure and is composed of a substrate, a conductive cathode, an electron transport layer, an organic photoactive layer, a hole transport layer and a metal anode from bottom to top.

[0010] The organic photoactive layer is prepared by adding a polymer donor PDPP3T, a fullerene acceptor PC 71 BM and a solvent additive 1,8-diiodooctane into an organic solvent to prepare a solution, and then preparing by a spin coating method, and removing the additive 1,8-diiodooctane and the organic solvent to obtain the photoactive layer.

[0011] Preferably, the mass ratio of the polymer donor PDPP3T and the fullerene acceptor PC 71 BM is 1:2; and the additive 1,8-diiodooctane accounts for 1.5-3% of the volume of the organic solvent.

[0012] Preferably, the total concentration of the polymer donor PDPP3T and the fullerene acceptor PC 71 BM in the spin coating solution is 5-20 g / mL; and the organic solvent is chlorobenzene.

[0013] Preferably, the additive 1,8-diiodooctane and the organic solvent are removed by a vacuum removal method; and the vacuum time is ≥7 h; more preferably 12 h.

[0014] The structural formula of the polymer donor PDPP3T of the organic photoactive layer is as follows:

[0015]

[0016] The structural formula of the fullerene acceptor of the organic photoactive layer is as follows:

[0017]

[0018] Preferably, the thickness of the organic photoactive layer is 300-800 nm; and the area is 0.04-100 cm 2 .

[0019] Preferably, the substrate is at least one of glass, a PET film and a polyimide film, and the thickness is 0.5-1.5 mm.

[0020] Preferably, the conductive cathode is at least one of indium tin oxide and fluorine tin oxide, and the thickness is 120-300 nm.

[0021] Preferably, the electron transport layer is a single interface layer of zinc oxide or a composite interface layer of 0.05-0.2 wt% (of zinc oxide) ethoxylated polyethyleneimine (PEIE) doped ZnO; the structure of the ethoxylated polyethyleneimine (PEIE) is as follows:

[0022]

[0023] More preferably, the thickness of the electron transport layer is also 30-50 nm.

[0024] Preferably, the hole transport layer is molybdenum oxide, and the thickness is 5-30 nm; more preferably, 5-10 nm.

[0025] Preferably, the metal anode is at least one of Ag, Al and Au, and the thickness is 80-100 nm.

[0026] More preferably, the metal anode top electrode is Ag, and the thickness is 80 nm.

[0027] Preferably, the hole transport layer and the metal anode are constructed by a thermal deposition method through a vacuum evaporation system.

[0028] The preparation method of the high specific detectivity optical detection device comprises the following steps:

[0029] (1) preparing an electron transport layer on a substrate / conductive cathode;

[0030] (2) preparing an organic photoactive layer on the electron transport layer by a spin coating method;

[0031] (3) sequentially depositing a hole transport layer and a metal anode on the organic photoactive layer.

[0032] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0033] (1) The present application prepares an additive-optimized high specific detectivity optical detection device; the preparation method is simple and feasible.

[0034] (2) The organic photoelectric detector significantly reduces the dark current of the detection device, and obtains a dark current density lower than 1.1×10 -10 cm -2 at a working voltage of -0.1 V. For incident light with a wavelength of 850 nm, the device obtains a specific detectivity higher than 4.8×10 13 Jones, realizing an optical detection device with low dark current and high specific detectivity.

[0035] (3) The organic photoelectric detector described in the present application has a detection rate 4 times higher than the same type, and has great application prospects in future research and engineering applications. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 is the dark current test result graph of the organic photoelectric detector of the present application in which the electron transport layer contains PEIE and the active layer does not add DIO.

[0037] Figure 2 is the EQE test result graph of the organic photoelectric detector of the present application in which the electron transport layer contains PEIE and the active layer does not add DIO.

[0038] Figure 3 is the specific detection rate test result graph of the organic photoelectric detector of the present application in which the electron transport layer contains PEIE and the active layer does not add DIO.

[0039] Figure 4 is the dark current test result graph of the organic photoelectric detector of the present application in which the electron transport layer contains PEIE and the active layer adds 1.5% volume fraction DIO.

[0040] Figure 5 is the EQE test result graph of the organic photoelectric detector of the present application in which the electron transport layer contains PEIE and the active layer adds 1.5% volume fraction DIO.

[0041] Figure 6 is the specific detection rate test result graph of the organic photoelectric detector of the present application in which the electron transport layer contains PEIE and the active layer adds 1.5% volume fraction DIO.

[0042] Figure 7 is the dark current test result graph of the organic photoelectric detector of the present application in which the electron transport layer is pure ZnO and the active layer adds 1.5% volume fraction DIO.

[0043] Figure 8 is the EQE test result graph of the organic photoelectric detector of the present application in which the electron transport layer is pure ZnO and the active layer adds 1.5% volume fraction DIO.

[0044] Figure 9 is the specific detection rate test result graph of the organic photoelectric detector of the present application in which the electron transport layer is pure ZnO and the active layer adds 1.5% volume fraction DIO.

[0045] Figure 10is a dark current test result chart of an organic photodetector with the electron transport layer containing PEIE as described in Example 3 of the present application, and the active layer adding 3% volume fraction DIO.

[0046] Figure 11 is an EQE test result chart of an organic photodetector with the electron transport layer containing PEIE as described in Example 3 of the present application, and the active layer adding 3% volume fraction DIO.

[0047] Figure 12 is a specific detectivity test result chart of an organic photodetector with the electron transport layer containing PEIE as described in Example 3 of the present application, and the active layer adding 3% volume fraction DIO.

[0048] Figure 13 is a dark current test result chart of an organic photodetector with the anode transport layer PEDOT:PSS and the cathode transport layer PDINO as described in Comparative Example 2 of the present application, and the active layer adding 1.5% volume fraction DIO.

[0049] Figure 14 is an EQE test result chart of an organic photodetector with the anode transport layer PEDOT:PSS and the cathode transport layer PDINO as described in Comparative Example 2 of the present application, and the active layer adding 1.5% volume fraction DIO. DETAILED DESCRIPTION

[0050] The present application will be further described in detail by the following examples and drawings, but the embodiments of the present application are not limited thereto.

[0051] In the embodiments of the present application, the specific conditions not mentioned are carried out according to the conventional conditions or the conditions recommended by the manufacturers. The raw materials, reagents and the like not mentioned by the manufacturers are all the conventional products which can be purchased in the market.

[0052] Comparative Example 1 (organic photodetector with the electron transport layer containing PEIE, and the active layer not adding DIO)

[0053] 1. Cleaning of ITO conductive glass: the ITO substrate is cleaned by ultrasonic cleaning with deionized water, acetone and isopropanol for 30 minutes respectively, and then is placed in a drying oven at 70°C for drying and preservation.

[0054] 2. Preparation of the cathode transport layer: 1 g of zinc acetate was mixed with 280 μL of ethanolamine, 10 mL of ethylene glycol methyl ether, and 2.7 μL of a 37% (w / w) PEIE aqueous solution and heated at 60 °C for 9 hours to obtain a zinc oxide solution doped with 0.1 wt% PEIE. An ITO substrate was placed on a spin coater, and the dissolved zinc oxide solution was evenly coated onto the ITO surface. The coating was then spin-coated at 3000 rpm for 30 s to obtain a zinc oxide film with a thickness of approximately 40 nm. The substrate was then placed on a heating stage and baked at 200 °C for one hour. After baking, the ITO substrate was transferred to a nitrogen-filled glove box for later use.

[0055] 3. Preparation of organic photoactive layer: PDPP3T:PC 71 The mass ratio of BM was 1:2, the processing solvent was chlorobenzene, the total concentration was 15 mg / ml, the spin coating speed was 1000 rpm, and the film thickness was 500 nm.

[0056] 4. Deposition of the hole transport layer: The substrate is transferred to a vacuum evaporation chamber, and the vacuum level is reduced to below 4 × 10⁻⁶. -6 Then, the molybdenum oxide is heated to deposit it on top of the active layer, with a thickness of about 8 nm.

[0057] 5. Deposition of metal anode: After the hole transport layer is deposited, the deposition of molybdenum oxide is turned off, and silver particles are heated to deposit them above the active layer with a thickness of about 80 nm.

[0058] The photodetector performance of this device was tested at an operating voltage of -0.1V, achieving a result lower than 6×10⁻⁶. -10 cm -2 The dark current density is [value missing]. For incident light at a wavelength of 850 nm, the device achieves a dark current density exceeding 1.1 × 10⁻⁶. 13 Jones's specific detection rate.

[0059] Example 1 (Organic photodetector with PEIE electron transport layer and 1.5% volume fraction DIO added to active layer)

[0060] 1. Cleaning of ITO conductive glass: The ITO substrate was ultrasonically cleaned for 30 minutes each with deionized water, acetone, and isopropanol. After cleaning, it was placed in a drying oven at 70°C to dry and store.

[0061] 2. Preparation of cathode transport layer: 1 g of zinc acetate was dissolved in 280 microliters of ethanolamine, 10 milliliters of ethylene glycol methyl ether and 2.7 microliters of 37% mass fraction of PEIE aqueous solution, heated and stirred at 60°C for 9 hours to obtain a 0.1wt% PEIE doped zinc oxide solution. The ITO substrate treated by oxygen plasma for 5 minutes was placed on the glue machine, and the dissolved zinc oxide solution was evenly coated on the ITO surface and spin-coated at 3000 rpm for 30 s to obtain a PEIE doped zinc oxide film with a thickness of about 40 nm. Then the substrate was placed on the heating table at 200°C for one hour, and after cooling, the ITO substrate was transferred into a nitrogen-filled glove box for standby.

[0062] 3. Preparation of organic photoactive layer: PDPP3T:PC 71 The mass ratio of BM is 1:2, the processing solvent is chlorobenzene, the volume fraction of DIO in chlorobenzene is 1.5%, the total concentration is 15 mg / ml, the spin-coating speed is 1000 rpm, the film thickness is 500 nm, and after film formation, it is placed in a vacuum chamber for 12 hours to extract additives.

[0063] 4. Deposition of hole transport layer: The substrate was transferred to the vacuum evaporation chamber, and the vacuum degree was extracted to 4x10 -6 After that, the molybdenum oxide was heated to be deposited above the active layer with a thickness of about 8 nm.

[0064] 5. Deposition of metal anode: After the hole transport layer was deposited, the molybdenum oxide deposition was turned off, and the silver particles were heated to be deposited above the active layer with a thickness of about 80 nm.

[0065] The light detection performance of the device was tested, and a dark current density lower than 1.1x10 -10 A·cm -2 was obtained at a working voltage of-0.1V. For incident light with a wavelength of 850 nm, the device obtained a specific detectivity of more than 4.8x10 13 cmHz 1 / 2 W -1 , realizing the highest specific detectivity and the lowest dark current of the light detection device.

[0066] Example 2 (organic photoelectric detector with pure ZnO as electron transport layer and 1.5% volume fraction of DIO added to the active layer)

[0067] 1. Cleaning of ITO conductive glass: The ITO substrate was ultrasonically cleaned with deionized water, acetone and isopropanol for 30 minutes respectively, and then placed in a 70°C drying oven for drying and storage.

[0068] 2. Preparation of cathode transport layer: 1 g of zinc acetate was mixed with 280 microliters of ethanolamine, 10 milliliters of ethylene glycol methyl ether and heated at 60°C for 9 hours to obtain a pure zinc oxide solution. The ITO substrate treated by oxygen plasma for 5 minutes was placed on a spin coater, and the dissolved zinc oxide solution was evenly coated on the ITO surface and spin-coated at 3000 rpm for 30 s to obtain a zinc oxide film with a thickness of about 40 nm. The substrate was then placed on a heating table at 200°C for one hour, and after cooling, the ITO substrate was transferred into a nitrogen-filled glove box for standby.

[0069] 3. Preparation of organic photoactive layer: PDPP3T:PCBM 71 The mass ratio of BM was 1:2, the processing solvent was chlorobenzene, the volume fraction of DIO in chlorobenzene was 1.5%, the total concentration was 15 mg / ml, the spin-coating speed was 1000 rpm, the film thickness was 500 nm, and after film formation, the substrate was placed in a vacuum chamber for 12 hours to extract the additive.

[0070] 4. Deposition of hole transport layer: The substrate was transferred to a vacuum evaporation chamber, and the vacuum degree was extracted to 4x10 -6 After that, the molybdenum oxide was heated to deposit on the active layer with a thickness of about 8 nm.

[0071] 5. Deposition of metal anode: After the hole transport layer was deposited, the molybdenum oxide deposition was turned off, and the silver particles were heated to deposit on the active layer with a thickness of about 80 nm.

[0072] The light detection performance of the device was tested, and a dark current density of less than 4x10 -10 A·cm -2 was obtained at a working voltage of -0.1 V. For incident light with a wavelength of 850 nm, the device obtained a specific detectivity of more than 3x10 13 cmHz 1 / 2 W -1 .

[0073] Comparative Example 2 (anode transport layer is PEDOT:PSS, cathode transport layer is PDINO, upright structure, active layer is added with 1.5% volume fraction of DIO organic photodetector)

[0074] 1. Cleaning of ITO conductive glass: The ITO substrate was ultrasonically cleaned with deionized water, acetone and isopropanol for 30 minutes respectively, and then placed in a 70°C drying oven for drying and storage.

[0075] 2. Preparation of anode transport layer: spin-coat PEDOT:PSS solution on ITO substrate which was surface treated by oxygen plasma for 5 minutes at 3000 rpm for 30 s to get a thin film with thickness of about 30 nm. Then put the substrate on a hot plate to bake at 150 °C for 15 min. After cooling, transfer the ITO substrate into a nitrogen-filled glove box for later use.

[0076] 3. Preparation of organic photoactive layer: PDPP3T:PCBM 71 The mass ratio of BM is 1:2, the processing solvent is chlorobenzene, the volume fraction of DIO in chlorobenzene is 1.5%, the total concentration is 15 mg / ml, the spin-coating speed is 1000 rpm, the film thickness is 500 nm, and the substrate is placed in a vacuum chamber for 12 hours after film formation.

[0077] 4. Preparation of cathode transport layer: spin-coat 2 mg / ml PDINO on the active layer after DIO extraction at 2500 rpm for 30 s to get a thin film with thickness of about 8 nm.

[0078] 5. Deposition of metal anode: transfer the substrate into a vacuum evaporation chamber, and extract the vacuum degree to 4x10 -6 After that, heat the silver particles to deposit on the device, with a thickness of about 80 nm.

[0079] Test the light detection performance of the device. The obtained dark current density is only 1.46x10 - 6 A·cm -2 . EQE is not more than 15%. It shows that the material is not suitable for preparing a commonly used inverted structure system.

[0080] Example 3 (organic photodetector with PEIE in the electron transport layer and 3% volume fraction of DIO in the active layer)

[0081] 1. Cleaning of ITO conductive glass: the ITO substrate is ultrasonically cleaned with deionized water, acetone and isopropanol for 30 minutes respectively, and then placed in a drying oven at 70 °C for drying and storage.

[0082] 2. Preparation of cathode transport layer: prepare a 0.1 wt% PEIE-doped zinc oxide solution by heating 1 g of zinc acetate with 280 microliters of ethanolamine, 10 milliliters of ethylene glycol methyl ether and 2.7 microliters of 37% mass fraction PEIE aqueous solution at 60 °C for 9 hours. Place the ITO substrate which was surface treated by oxygen plasma for 5 minutes on a spin coater, evenly apply the dissolved zinc oxide solution on the ITO surface, and spin-coat at 3000 rpm for 30 s to get a thin film of PEIE-doped zinc oxide with thickness of about 40 nm. Then place the substrate on a hot plate to bake at 200 °C for one hour. After cooling, transfer the ITO substrate into a nitrogen-filled glove box for later use.

[0083] 3. Preparation of organic photoactive layer: PDPP3T:PCBM 71 The mass ratio of BM was 1:2, the processing solvent was chlorobenzene, the volume fraction of DIO in chlorobenzene was 3%, the total concentration was 15 mg / ml, the spin coating speed was 1000 rpm, the film thickness was 500 nm, and after film formation, the sample was placed in a vacuum chamber for 12 hours to extract the additive.

[0084] 4. Deposition of hole transport layer: the substrate was transferred to a vacuum evaporation chamber, and the vacuum degree was extracted to 4x10 -6 After that, the molybdenum oxide was heated to deposit on the active layer with a thickness of about 8 nm.

[0085] 5. Deposition of metal anode: after the deposition of the hole transport layer was completed, the molybdenum oxide deposition was closed, and the silver particles were heated to deposit on the active layer with a thickness of about 80 nm.

[0086] The light detection performance of the device was tested, and a dark current density lower than 8x10 -10 A·cm -2 was obtained at a working voltage of -0.1 V. For incident light with a wavelength of 850 nm, the device obtained a specific detectivity of more than 1.6x10 13 cmHz 1 / 2 W -1 .

[0087] The above examples are the preferred embodiments of the present application, but the embodiments of the present application are not limited by the above examples, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application are equivalent replacement methods, which are all included in the protection scope of the present application.

Claims

1. A high specific detectivity photodetector, characterized in that, Its flip-chip structure consists of a substrate, a conductive cathode, an electron transport layer, an organic photoactive layer, a hole transport layer, and a metal anode, from bottom to top. The organic photoactive layer is prepared by the following method: polymer donor PDPP3T and fullerene acceptor PC are mixed. 71 BM and solvent additive 1,8-diiodooctane were added to an organic solvent to prepare a solution, which was then prepared by spin coating. After removing the additive 1,8-diiodooctane and the organic solvent, a photoactive layer was obtained. The electron transport layer is a composite interface layer of 0.05-0.2 wt% ethoxylated polyethyleneimine doped with ZnO; The additive 1,8-diiodooctane accounts for 1.5 to 3% of the volume of the organic solvent.

2. The high specific detectivity photodetector device according to claim 1, characterized in that, The polymer donor PDPP3T and fullerene acceptor PC 71 The mass ratio of BM is 1:

2.

3. The high specific detectivity photodetector device according to claim 1, characterized in that, The thickness of the electron transport layer is 30–50 nm.

4. The high specific detectivity photodetector device according to claim 1, characterized in that, The removal of additive 1,8-diiodooctane and organic solvent is performed by vacuum removal; the vacuum time is ≥7h.

5. A high specific detectivity photodetector device according to claim 1, characterized in that, The solution contains polymer donor PDPP3T and fullerene acceptor PC. 71 The total concentration of BM in the spin-coating solution is 5–20 mg / mL; the organic solvent is chlorobenzene.

6. The high specific detectivity photodetector device according to claim 1, characterized in that, The additive 1,8-diiodooctane accounts for 1.5% of the volume of the organic solvent; the electron transport layer is a composite interface layer of 0.05-0.2 wt% ethoxylated polyethyleneimine doped with ZnO.

7. The high specific detectivity photodetector device according to claim 1, characterized in that, The thickness of the organic photoactive layer is 300–800 nm; The conductive cathode is at least one of indium tin oxide and fluorine tin oxide, and its thickness is 120-300 nm. The substrate is at least one of glass, PET film and polyimide film, with a thickness of 0.5 to 1.5 mm.

8. The high specific detectivity photodetector device according to claim 1, characterized in that, The hole transport layer is molybdenum oxide, and its thickness is 5–30 nm. The metal anode is at least one of Ag, Al and Au, and has a thickness of 80-100 nm.

9. A method for fabricating a high specific detectivity photodetector according to any one of claims 1 to 8, characterized in that, Includes the following steps: (1) An electron transport layer is fabricated on a substrate / conductive cathode; (2) An organic photoactive layer was prepared on the electron transport layer by spin coating; (3) A hole transport layer and a metal anode are sequentially deposited on the organic photoactive layer.

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