Method for realizing multiplication type photoelectric detector and up-conversion luminescent device

Abstract

The invention discloses a method for realizing a multiplication type photoelectric detector and an up-conversion luminescent device, which can realize the effect that the external quantum efficiency (EQE) exceeds 10000% only by using an external voltage of-1V (-0.8 to 1.2 V), and the photoelectric multiplication type photoelectric detector is directly integrated on a light-emitting diode to obtain the up-conversion luminescent device. And the imaging effect of the up-conversion luminescent device is greatly improved. The method for realizing the multiplication type photoelectric detector specifically comprises the step of sequentially preparing the metal top electrode, the infrared absorption layer, the electron transport layer I, the transparent conductive bottom electrode and the glass substrate from top to bottom to obtain the multiplication type photoelectric detector. Wherein the preparation mode of the electron transport layer I is as follows: after the ZnO thin film layer is treated by a 2wt% acetic acid-methanol solution, interface oxygen vacancy is introduced into the ZnO thin film layer, so that the ZnO thin film layer is used as the electron transport layer I. And a high-efficiency up-conversion luminescent device is prepared based on the multiplication type photoelectric detector.

Description

Technical Field

[0001] The invention relates to the field of photoelectric detector technology and up-conversion luminescence technology, and in particular to a method for realizing a multiplication type photoelectric detector and an up-conversion luminescence device. Background Art

[0002] Infrared photodetectors have aroused great research interest due to their wide application in various advanced optoelectronic systems, such as detection and imaging, optical interconnection systems, optical communications, and biosensors. Generally, high-performance infrared photodetectors are mainly made of materials such as HgCdTe or InGaAs. However, their high production costs limit their commercial applications. Therefore, developing cheap infrared photodetectors by selecting low-cost materials that can absorb infrared light is a key solution. Narrow bandgap semiconductor quantum dot nanomaterials, especially lead sulfide (PbS) and lead selenide (PbSe) colloidal quantum dots (CQDs), are often used in the application of infrared photodetectors due to their adjustable bandgap, simple synthesis methods, and low cost. In addition, PbS and PbSe colloidal quantum dots can be processed in solution and show strong light absorption ability, which is very competitive in low-cost short-wave infrared photodetectors. For example, Chinese patent CN110311007B and Chinese patent CN102110736B both disclose a near-infrared detector based on PbS colloidal quantum dots.

[0003] It is generally believed that photodetectors can be divided into several types, such as photoconductivity, photodiodes, phototransistors, and photomultipliers. In addition to the most widely studied and applied photoconductivity and photodiodes, photomultipliers have recently been frequently used in organic semiconductors because they involve charge multiplication caused by electrons generated by impact ionization. So far, previously reported photomultipliers are mainly based on the working mechanism of charge tunneling injection caused by interface traps. Carriers will be generated in the absorption layer under light, and electrons (or holes) will be trapped in the interface traps. These trapped electrons (or holes) generate a Coulomb field that causes the energy band to bend at the interface, so that the opposite charge carriers from the external circuit can tunnel through the potential barrier and be injected into the material layer. Under the irradiation of incident light, the tunneling injection of electrons (or holes) can lead to a carrier multiplication effect, and its external quantum efficiency (EQE) exceeds 100%. The external quantum efficiency of existing photodetectors is relatively low. To achieve an external quantum efficiency (EQE) of more than 100%, a relatively high external voltage (-20V and above) is required when using existing photodetectors.

[0004] How to achieve high external quantum efficiency of photodetectors under low applied voltage is an urgent problem to be solved. Summary of the invention

[0005] In view of this, the present invention provides a method for realizing an amplified photodetector and an up-conversion light-emitting device, which can achieve an external quantum efficiency (EQE) of more than 10000% under an applied voltage of only -1V (-0.8~1.2V), and directly integrates the photomultiplier photodetector on a light-emitting diode to prepare an up-conversion light-emitting device, greatly improving the imaging effect of the up-conversion light-emitting device.

[0006] To achieve the above objectives, the technical solution of the present invention is: a method for realizing an amplification type photodetector, preparing a metal top electrode, an infrared absorption layer, an electron transport layer 1, a transparent conductive bottom electrode and a glass substrate from top to bottom to obtain an amplification type photodetector.

[0007] The electron transport layer is prepared by treating the ZnO thin film layer with a 2 wt % acetic acid-methanol solution, and then introducing interface oxygen vacancies into the ZnO thin film layer to form the electron transport layer.

[0008] Furthermore, a metal top electrode, an infrared absorption (active) layer, an electron transport layer 1, a transparent conductive bottom electrode and a glass substrate are prepared in sequence from top to bottom to obtain an amplification type photodetector.

[0009] The specific steps include:

[0010] (1) A ZnO material is synthesized by a sol-gel method, and the obtained ZnO material is spin-coated on a transparent conductive bottom electrode by an annealing recrystallization method to prepare an electron transport layer 1; the transparent conductive bottom electrode is fixed on a glass substrate.

[0011] (2) The PbS colloidal quantum dot solution is spin-coated on the electron transport layer 1 by a spin coating method to prepare an infrared absorption (active) layer.

[0012] (3) On the infrared absorption (active) layer, a metal top electrode is prepared by using a mask and a thermal evaporation method to obtain a multiplication type photodetector.

[0013] Furthermore, the infrared absorption (active) layer is a lead sulfide or lead selenide colloidal quantum dot material, and the spin coating speed of the infrared absorption layer is 2000rpm to 4000rpm, and the spin coating time is 30s to 90s.

[0014] Furthermore, the preparation method of the ZnO thin film as the electron transport layer is to synthesize a high-quality ZnO thin film layer by combining a sol-gel method and annealing recrystallization. The steps of the method are as follows:

[0015] Zinc acetate dihydrate [Zn(Ac)2·2H2O] was mixed evenly in a solution of ethylene glycol methyl ether and ethanolamine in a volume ratio of 24:1 and spin-coated onto an ITO glass substrate. The ITO glass substrate was then annealed at 300°C for 10 minutes, at which time Zn(Ac)2 was converted into ZnO.

[0016] The surface of the ZnO film is cleaned by spin coating with an acetic acid-methanol solution, and the ZnO film is rinsed with isopropanol, acetone and ethanol, and finally dried at 200° C. for 10 minutes, at which time oxygen vacancies are introduced on the surface of the ZnO film layer.

[0017] Furthermore, the concentration of the zinc acetate dihydrate solution is 0.4M to 0.6M.

[0018] Furthermore, the thickness of the metal top electrode is 30nm to 150nm, the thickness of the electron transport layer 1 is 20nm to 150nm, the thickness of the infrared absorption (active) layer is 100nm to 800nm, and the thickness of the transparent conductive bottom electrode is 50nm to 180nm.

[0019] Another embodiment of the present invention also provides an up-conversion light-emitting device for realizing a multiplication-type photodetector, comprising a metal top electrode, an electrode modification layer, an electron transport layer 2, a light-emitting layer, a hole transport layer, an infrared absorption layer, an electron transport layer 1, and a transparent conductive bottom electrode, which are prepared in sequence from top to bottom; wherein the electron transport layer 1 is a ZnO thin film layer with interface oxygen vacancies introduced as described in claim 1.

[0020] Furthermore, the thickness of the electrode modification layer is 0.5nm-5nm, the thickness of the hole transport layer is 10nm-100nm, the thickness of the light-emitting layer is 30nm-100nm, the thickness of the electron transport layer 1 is 20nm-150nm, and the thickness of the electron transport layer 2 is 10nm-100nm.

[0021] Furthermore, the hole transport layer in the organic light emitting diode is 1-bis[4-[N,NN-di(4-methylphenyl)amino]phenyl]-cyclohexane (TAPC).

[0022] Preferably, the light-emitting layer in the organic light-emitting diode is 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP) and tris(2-phenylpyridine)iridium [Ir(ppy) 3 ].

[0023] Preferably, the weight ratio of the two materials in the CBP and Ir(ppy) 3 mixture layer is 93:7.

[0024] Preferably, the second electron transport layer in the organic light emitting diode is bathocuproine (BCP).

[0025] Preferably, the electrode modification layer in the organic light emitting diode is lithium fluoride (LiF).

[0026] Furthermore, the metal top electrode Al, and the transparent conductive bottom electrode are indium tin oxide (ITO).

[0027] Beneficial Effects :

[0028] (1) The present invention provides a method for realizing a multiplication type photodetector, wherein an appropriate amount of acetic acid is added to a ZnO thin film layer to introduce some oxygen vacancies on the surface of the ZnO thin film, and the concentration of acetic acid is optimized to appropriately bend the energy band of the ZnO thin film layer, thereby enabling the photodetector to have a mechanism for generating a photomultiplier effect. Using technologies such as an X-ray photoelectron spectrometer (XPS), the present invention experimentally confirms the existence of oxygen vacancies on the interface of the ZnO thin film layer; and the prepared multiplication type photodetector can achieve an external quantum efficiency (EQE) of more than 10,000% at an applied voltage of only -1V (-0.8 to 1.2V).

[0029] (2) The present invention prepares an ultra-sensitive up-conversion light-emitting device based on a multiplication-type photodetector, which greatly improves the imaging effect of the up-conversion light-emitting device and has significant cost and energy consumption advantages, and thus has significant application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 (a) is a schematic diagram of the structure of an amplification type photodetector realized by introducing interfacial oxygen vacancies into the ZnO layer as described in Example 1 of the present invention; Figure 1 (b) is a schematic diagram of the structure of an ultra-sensitive upconversion light-emitting device realized by introducing interfacial oxygen vacancies in the ZnO layer as described in Example 2 of the present invention; the ITO lower layer is a 1 mm thick glass substrate.

[0031] Figure 2 is an X-ray photoelectron spectrum of the ZnO thin film in Comparative Example 1 of the present invention;

[0032] Figure 3 is an X-ray photoelectron spectrum of the ZnO-1 thin film in Comparative Example 2 of the present invention;

[0033] Figure 4 is an X-ray photoelectron spectrum of the ZnO-2 thin film in Example 1 of the present invention;

[0034] Figure 5 is an X-ray photoelectron spectrum of the ZnO-3 thin film in Comparative Example 3 of the present invention;

[0035] Figure 6It is a transmission electron microscope photo and an electron energy loss spectrum of the ZnO-2 film corrected for double spherical aberration in Example 1 of the present invention;

[0036] Figure 7 Schematic diagram of the energy band structure of the multiplication type photodetector prepared based on the ZnO thin film in comparative example 1 of the present invention in the dark (ie without light irradiation);

[0037] Figure 8 It is a schematic diagram of the energy band structure of the multiplication type photodetector prepared based on the ZnO thin film described in Comparative Example 1 of the present invention under 980nm infrared light illumination;

[0038] Fig. 9 Schematic diagram of the energy band structure of the multiplication type photodetector prepared based on the ZnO-2 thin film in the dark according to Example 1 of the present invention;

[0039] Fig.10 It is a schematic diagram of the energy band structure of the multiplication type photodetector prepared based on the ZnO-2 thin film described in Example 1 of the present invention under 980nm infrared light illumination;

[0040] Fig.11 The ultraviolet photoelectron spectroscopy (UPS) data of ZnO, ZnO-1, ZnO-2, ZnO-3 and PbS materials described in Example 1 and Comparative Examples 1-3 of the present invention; (ac) are valence band diagrams, UPS diagrams and secondary cutoff edge diagrams of ZnO thin films, respectively; (df) are valence band diagrams, UPS diagrams and secondary cutoff edge diagrams of ZnO-1 thin films, respectively; (gi) are valence band diagrams, UPS diagrams and secondary cutoff edge diagrams of ZnO-2 thin films, respectively; (jl) are valence band diagrams, UPS diagrams and secondary cutoff edge diagrams of ZnO-3 thin films, respectively; (mo) are valence band diagrams, UPS diagrams and secondary cutoff edge diagrams of PbS thin films, respectively;

[0041] Fig.12 This is the IV curve of the multiplication type photodetector based on ZnO thin film in comparative example 1 of the present invention under 980nm infrared light; the infrared light irradiation intensity from top to bottom on the left is 1.637mW / cm 2 、285μW / cm 2 、13.9μW / cm 2 , 1.9μW / cm 2 and 0.2μW / cm 2 And IV curve of dark current;

[0042] Fig.13 This is the IV curve of the multiplication type photodetector based on ZnO-1 thin film in comparative example 2 of the present invention under 980nm light irradiation; the light intensity from top to bottom on the left is 1.637mW / cm2 、285μW / cm 2 、13.9μW / cm 2 , 1.9μW / cm 2 and 0.2μW / cm 2 And IV curve of dark current;

[0043] Fig.14 This is the IV curve of the light multiplication type photodetector based on ZnO-2 thin film prepared in Example 1 of the present invention under light with a wavelength of 980nm; the light intensity from top to bottom on the left is 1.637mW / cm 2 、285μW / cm 2 、13.9μW / cm 2 , 1.9μW / cm 2 and 0.2μW / cm 2 And IV curve of dark current;

[0044] Fig.15 This is the IV curve of the multiplication type photodetector prepared based on ZnO-3 thin film in comparative example 3 of the present invention under 980nm light irradiation; the light intensity from top to bottom on the left is 1.637mW / cm 2 、285μW / cm 2 、13.9μW / cm 2 , 1.9μW / cm 2 and 0.2μW / cm 2 And IV curve of dark current;

[0045] Fig.16 It is a responsivity diagram of the multiplication type photodetector described in Example 1 and Comparative Examples 1-3 of the present invention under irradiation with 980nm light of different incident light power densities;

[0046] Fig.17 It is an external quantum efficiency diagram of the multiplication type photodetector described in Example 1 of the present invention and Comparative Examples 1-3 under irradiation of 980nm light with different incident light power densities;

[0047] Fig.18 1 is a graph of the detection ratio of the multiplication type photodetector described in Example 1 and Comparative Examples 1-3 of the present invention under irradiation with 980nm light of different incident light power densities;

[0048] Fig.19 It is a brightness diagram of the ultra-sensitive up-conversion light-emitting device described in Example 2 of the present invention and Comparative Examples 4-6 at different voltages. DETAILED DESCRIPTION

[0049] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0050] A method for realizing a multiplication type photodetector and its application in an upconversion light-emitting device. One of the photodetectors capable of realizing a multiplication effect belongs to a stacked device, which includes an electron transport layer, wherein the electron transport layer 1 is a ZnO thin film layer. After the ZnO thin film layer is treated with a 2wt% acetic acid-methanol solution, interfacial oxygen vacancies can be introduced into the ZnO thin film layer, so that the prepared photodetector has a photomultiplication mechanism. A method for realizing a multiplication type photodetector, comprising a metal top electrode (Ag in FIG.), an infrared absorption (active) layer (PbS), an electron transport layer 1 (ZnO), a transparent conductive bottom electrode and a glass substrate, which are prepared in sequence from top to bottom; wherein the electron transport layer 1 is a ZnO thin film layer with interfacial oxygen vacancies introduced as described in the present invention.

[0051] Preferably, the acetic acid-methanol solution is 2 wt % (weight ratio).

[0052] Preferably, the infrared absorption layer is lead sulfide (or lead selenide) colloidal quantum dot material.

[0053] A method for realizing a multiplication type photodetector. The preparation method of the ZnO thin film as the electron transport layer is to synthesize a high-quality ZnO thin film layer by combining a sol-gel method and annealing recrystallization. The steps of the method are as follows:

[0054] Zinc acetate dihydrate [Zn(Ac)2·2H2O] was mixed evenly in a solution of ethylene glycol methyl ether and ethanolamine in a volume ratio of 24:1 and spin-coated onto an ITO glass substrate. The ITO glass substrate was then annealed at 300°C for 10 minutes, at which time Zn(Ac)2 was converted into ZnO.

[0055] The surface of the ZnO film is cleaned by spin coating with an acetic acid-methanol solution (acetic acid-methanol or ethanol), and the ZnO film is rinsed with isopropanol, acetone and ethanol (three kinds), and finally dried at 200°C for 10 minutes (after drying), at which time oxygen vacancies are introduced on the surface of the ZnO film layer.

[0056] Preferably, the concentration of the zinc acetate dihydrate solution is 0.4M to 0.6M.

[0057] A method for realizing an amplification-type photodetector, comprising a metal top electrode (Ag in FIG. ), an infrared absorption (active) layer (PbS), an electron transport layer (ZnO-2), a transparent conductive bottom electrode (ITO), and a glass substrate, which are prepared in sequence from top to bottom; wherein the electron transport layer is a ZnO thin film layer with interface oxygen vacancies introduced as described in the present invention.

[0058] Preferably, the thickness of the metal top electrode is 30nm to 150nm, the thickness of the electron transport layer 1 is 20nm to 150nm, the thickness of the infrared absorption layer is 100nm to 800nm, and the thickness of the transparent conductive bottom electrode is 50nm to 180nm.

[0059] Preferably, the method for realizing a multiplication type photoelectric detector can be prepared by the following method, and the steps of the method include:

[0060] (1) synthesizing ZnO material by a sol-gel method, and spin-coating the obtained ZnO material on a transparent conductive bottom electrode substrate by an annealing recrystallization method to prepare an electron transport layer 1;

[0061] (2) spin coating a PbS colloidal quantum dot solution on the electron transport layer 1 to prepare an infrared absorption layer;

[0062] (3) On the infrared absorption layer, a metal top electrode is prepared by using a mask and a thermal evaporation method to obtain an amplification type photodetector.

[0063] Preferably, in step (2), the spin coating speed of the infrared absorption layer is 2000 rpm to 4000 rpm, and the spin coating time is 30 s to 90 s.

[0064] An ultra-sensitive upconversion light-emitting device, the upconversion device is composed of a photodetector and an organic light-emitting diode; from top to bottom, it includes a metal top electrode, an electrode modification layer, an electron transport layer 2, a light-emitting layer, a hole transport layer (HTL), an infrared absorption layer, an electron transport layer 1 and a transparent conductive bottom electrode; wherein the electron transport layer 1 is a ZnO thin film layer introduced with interface oxygen vacancies as described in the present invention.

[0065] Preferably, the hole transport layer in the organic light emitting diode is 1-bis[4-[N,NN-di(4-methylphenyl)amino]phenyl]-cyclohexane (TAPC).

[0066] Preferably, the light-emitting layer in the organic light-emitting diode is 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP) and tris(2-phenylpyridine)iridium [Ir(ppy) 3 ].

[0067] Preferably, the weight ratio of the two materials in the CBP and Ir(ppy) 3 mixture layer is 93:7.

[0068] Preferably, the second electron transport layer in the organic light emitting diode is bathocuproine (BCP).

[0069] Preferably, the electrode modification layer in the organic light emitting diode is lithium fluoride (LiF).

[0070] Preferably, the metal top electrode is Al, and the transparent conductive bottom electrode is indium tin oxide (ITO).

[0071] Preferably, the thickness of the electrode modification layer is 0.5nm-5nm, the thickness of the hole transport layer is 10nm-100nm, the thickness of the light-emitting layer is 30nm-100nm, the thickness of the electron transport layer 1 is 20nm-150nm, and the thickness of the electron transport layer 2 is 10nm-100nm.

[0072] Preferably, the ultra-sensitive up-conversion light-emitting device is prepared by the following method, the steps of which include:

[0073] (1) ZnO is synthesized by a sol-gel method, then spin-coated on a transparent conductive bottom electrode substrate, and an electron transport layer 1 is prepared by an annealing recrystallization method;

[0074] (2) spin coating a PbS colloidal quantum dot solution on the electron transport layer 1 by a spin coating method to prepare an infrared absorption layer;

[0075] (3) On the infrared absorption layer, a hole transport layer is prepared by thermal evaporation using a mask.

[0076] (4) On the hole transport layer, an organic light-emitting layer is prepared by thermal evaporation using a mask.

[0077] (5) On the light-emitting layer, a second electron transport layer is prepared by thermal evaporation using a mask.

[0078] (6) On the second electron transport layer, an electrode modification layer is prepared by using a mask and a thermal evaporation method.

[0079] (7) On the electrode modification layer, a metal top electrode is prepared by a mask and thermal evaporation method, thereby obtaining an ultra-sensitive up-conversion light-emitting device.

[0080] In the following examples or comparative examples:

[0081] The absorption spectra of the nanomaterials were analyzed using a UV-Vis-NIR spectrophotometer (Shimadzu, UV-3600). The optoelectronic properties of the device were characterized in the dark (no light) and at different light intensities of 980 nm using a semiconductor parameter analysis system (Keithley 4200-SCS). The surface element state analysis of the device was tested using a photoelectron spectrometer (5000Versaprobe III). The brightness map of the device was tested using a scanning luminance meter (PR-655). The double spherical aberration corrected transmission electron microscope images of the material were taken using FEI Themis Z. The X-ray diffraction (XRD) pattern was recorded by Philips X'Pert Pro MPD. All characterizations were performed in air at room temperature.

[0082] Example 1

[0083] A method for preparing a ZnO thin film, which uses a sol-gel method combined with annealing and recrystallization to prepare a high-quality ZnO thin film, the steps of the method are as follows:

[0084] Zinc acetate dihydrate [Zn(Ac)2·2H2O] with a concentration of 0.5M was mixed evenly in a solution of ethylene glycol methyl ether and ethanolamine with a volume ratio of 24:1, and then spin-coated on the ITO glass at a rate of 2500rpm for 30 seconds. The ITO glass was then annealed at 300℃ for 10 minutes, at which time Zn(Ac)2 was converted into ZnO. The surface of the ZnO film was cleaned by spin coating with a 2wt% acetic acid-methanol solution, and the ZnO film was rinsed with isopropanol, acetone and ethanol, and finally dried at 200℃ for 10 minutes, at which time oxygen vacancies were introduced into the interface of the ZnO film. For the convenience of description, the ZnO film sample treated with a 2wt% acetic acid-methanol solution is recorded as ZnO-2.

[0085] A method for preparing PbS colloidal quantum dots, using a hot injection method to prepare high-quality PbS colloidal quantum dots, the method steps are as follows:

[0086] 8 mmol yellow lead oxide was dissolved in 240 mmol 1-octadecene (ODE) and 16 mmol oleic acid (OA), all of which were placed in a three-necked flask and stirred to make them fully dissolved. Stirring was continued at 150 ° C for 0.5 h, and all Pb 2+Should react with OA. Dissolve 4mmol hexamethyldisilathione in 64mL ODE, stir continuously at 60°C for 30 minutes, then quickly inject the hexamethyldisilathione solution into a three-necked flask and react at 120°C for 2 minutes. Subsequently, immediately cool the reactant with an ice water bath. Centrifuge the cooled crude solution at 7000rpm for 10 minutes. After centrifugation, separate and collect the particles, repeat three times to obtain PbS colloidal quantum dots. The PbS colloidal quantum dots have an absorption peak located in the near-infrared region.

[0087] A method for preparing a multiplication type photoelectric detector, the method steps are as follows:

[0088] (1) The 100 nm ITO patterned glass substrate was ultrasonically cleaned for 15 minutes using deionized water, isopropanol, acetone, and ethanol, respectively. A ZnO film was then prepared on the ITO and treated with a 2 wt% acetic acid-methanol solution to introduce oxygen vacancies at the interface of the ZnO film. The resulting sample was then treated under ultraviolet light for 30 minutes to obtain an electron transport layer.

[0089] (2) Prepare a PbS colloidal quantum dot solution with a concentration of 20 mg / mL in n-hexane as solvent, and spin-coat it on the electron transport layer at a speed of 2500 rpm for 30 seconds. Repeat 3-5 times until the thickness reaches 250 nm, thereby obtaining an infrared absorption layer.

[0090] (3) A 100 nm silver top electrode is evaporated onto the PbS layer through a mask to obtain a multiplication type photodetector, the specific structure of which is as follows: Figure 1 (a) shown.

[0091] Example 2

[0092] A method for preparing an ultra-sensitive up-conversion light-emitting device, the method comprising the following steps:

[0093] Steps (1) and (2) are the same as those in Example 1.

[0094] (3) The sample with ZnO thin film and PbS quantum dot active layer prepared on 18mm×18mm ITO glass substrate was transferred to the chamber of vacuum coating machine, and the chamber was kept in low oxygen environment to prevent oxygen from affecting the organic light-emitting diode material to be evaporated. Then, hole transport layer TPAC, CBP and Ir(ppy)3 emitting layer mixed in a weight ratio of 93:7, hole transport layer BCP, electrode modification layer LiF and Al electrode were prepared in sequence. The specific structure of the device is as follows: Figure 1 (b) as shown.

[0095] Example 3

[0096] The ITO glass used in this embodiment has an area of ​​30 mm×30 mm, and the rest is the same as in Embodiment 2.

[0097] Example 4

[0098] The ITO glass used in this embodiment has an area of ​​30 mm×30 mm and is composed of a 16×16 dot matrix of Embodiment 2. Each dot matrix is ​​a circular device with a diameter of 1 mm and a spacing of 0.5 mm. The rest is the same as Embodiment 2.

[0099] Comparative Example 1

[0100] In this embodiment, the acetic acid-methanol solution is not used to clean the ZnO surface, and the rest is the same as in Example 1. For the convenience of description, the sample whose ZnO film surface is not treated with the acetic acid-methanol solution is recorded as ZnO.

[0101] Comparative Example 2

[0102] In this embodiment, 1 wt % acetic acid-methanol solution was used to treat the surface of the ZnO film, and the rest of the conditions were the same as those in Embodiment 1. For the convenience of description, the sample in which the surface of the ZnO film was treated with 1 wt % acetic acid-methanol solution was recorded as ZnO-1.

[0103] Comparative Example 3

[0104] In this embodiment, 3 wt % acetic acid-methanol solution is used to treat the surface of the ZnO film, and the rest is the same as in Embodiment 1. For the convenience of description, the sample in which the surface of the ZnO film is treated with 3 wt % acetic acid-methanol solution is recorded as ZnO-3.

[0105] Comparative Example 4

[0106] In this embodiment, acetic acid-methanol solution is not used to treat the ZnO surface, and the rest is the same as in Embodiment 2.

[0107] Comparative Example 5

[0108] In this embodiment, 1 wt % acetic acid-methanol solution is used to treat the ZnO surface, and the rest is the same as in Embodiment 2.

[0109] Comparative Example 6

[0110] In this embodiment, 3 wt % acetic acid-methanol solution is used to treat the ZnO surface, and the rest is the same as in Embodiment 2.

[0111] The oxygen element XPS spectra of Comparative Example 1, Comparative Example 2, Example 1 and Comparative Example 3 are as follows Figure 2-5As shown, the sub-peak representing oxygen vacancies is 531.8eV, the content of oxygen vacancies in the ZnO sample not treated with acetic acid is 59.34%, and the content of oxygen in the ZnO-1 sample treated with 1wt% acetic acid-methanol increases to 71.73%. With the increase of acetic acid concentration, the oxygen content in ZnO-2 increases to 87.49%, and the oxygen content in ZnO-3 increases to 92.22%, which fully demonstrates that acetic acid treatment will add a lot of oxygen vacancies to the surface of ZnO.

[0112] The present invention confirms the existence of interfacial oxygen vacancies by double spherical aberration corrected transmission electron microscopy and EELS spectrum, such as Figure 6 As shown, by selecting a point at different depths of the ZnO film cross section of Example 1 and comparing its electron energy loss spectrum, it can be seen that the closer to the surface, the higher the proportion of oxygen vacancies, which confirms the existence of interfacial oxygen vacancies.

[0113] like Figure 7-10 As shown, the present invention compares in detail the energy band schematic diagrams of Comparative Example 1 and Example 1 in the dark state (without illumination) and with illumination.

[0114] Due to the high injection barrier at the ITO / ZnO interface, external holes cannot be injected into the ZnO layer, which inhibits the generation of photocurrent and photomultiplier effect. When the ZnO film is treated with acetic acid, more interfacial oxygen vacancies can be generated, which can capture electrons, so even in the dark, these trapped electrons will cause band bending at the ZnO / PbS interface. Under 980nm light irradiation, photogenerated electrons and holes can be generated in the PbS QD layer, with photogenerated holes flowing to the Ag electrode and photogenerated electrons flowing to the ZnO layer. The number of electrons captured by oxygen vacancies increases with the increase of incident light intensity, and the energy band gradually bends with the increase of the number of photogenerated electrons accumulated at the ZnO / PbS interface, resulting in a more obvious band bending. Although the depletion region becomes wider, the built-in electric field will produce a larger injection barrier compared to the case of no light and negative bias. In this way, holes can tunnel through the ZnO film layer into the device, enabling the device to achieve photomultiplication under light. Combined with Fig.11 The UPS results show that the Fermi level at the ZnO / PbS interface decreases with the accumulated photogenerated electrons, and the ZnO / PbS junction changes from a type I heterojunction to a type II heterojunction, which changes the direction of the built-in electric field. Therefore, the barrier for holes to enter the ZnO thin film layer is reduced, resulting in more holes tunneling and entering the ZnO thin film layer. As a result, the photocurrent increases, and the photomultiplier effect can enable the photodetector to obtain high gain.

[0115] The current-voltage curves of Comparative Example 1, Comparative Example 2, Example 1 and Comparative Example 3 are as follows Figures 12 to 15By comparison, it is found that the device treated with acetic acid has a larger photocurrent and photomultiplier effect, but when the ZnO film is treated with a 3wt% acetic acid-methanol solution, the dark current of the photodetector becomes larger. This may be due to excessive acetic acid corroding ZnO, making the device have a larger dark current and more likely to cause a short circuit in the device.

[0116] In order to evaluate the performance of the stacked self-driven photodetector, its key performance indicators, such as photoresponsivity (R), external quantum efficiency (EQE), specific detectivity (D * ) are described as follows:

[0117] (1) Photoresponsivity: The ratio of the photocurrent generated by the photodetector under illumination to the product of the incident light power and the effective area of ​​the device is defined as responsivity (R). R can directly reflect the photoelectric conversion capability of the photodetector and is an important measure of the spectral characteristics and frequency characteristics of the photoelectric conversion. Its calculation formula is:

[0118]

[0119] Among them I ill is the current of the device under illumination, I dark is the dark current generated by the device in the absence of light, and the difference between the two is the photocurrent I ph .P in is the incident light power per unit area (i.e., light intensity), and A is the effective area of ​​the device on which light is incident.

[0120] At 0.2 μW / cm 2 Under 980nm light irradiation, the multiplication type photodetector described in Example 1 obtained a responsivity of 524A / W at -1V. Fig.16 Its responsivity decreases with the increase of illumination power intensity.

[0121] (2) External quantum efficiency: The ratio of the number of electron-hole pairs generated per unit time to the number of incident photons is called external quantum efficiency (EQE). Its calculation formula is:

[0122]

[0123] Where R is the responsivity, h is Planck's constant, v is the frequency of the incident light, e is the elementary charge, c is the speed of light, and λ is the wavelength of the incident light.

[0124] At 0.2 μW / cm 2Under 980nm laser irradiation, the multiplication type photodetector described in Example 1 obtained an external quantum efficiency of 66515% at -1V. Fig.17 The improvement of external quantum efficiency fully demonstrates the successful preparation of this multiplication-type photodetector. Due to the external charge injection caused by interface defects, its external quantum efficiency far exceeds 100%.

[0125] (3) Specific detectivity: The signal-to-noise ratio obtained by a device under unit power radiation is called specific detectivity (D * ), also known as "normalized detectivity". It is a crucial performance parameter of photodetectors and an important means of measuring their sensitivity and detection capabilities. Its calculation formula is:

[0126]

[0127] Obviously, for a photodetector, the higher its specific detection rate, the higher its ability to detect light signals.

[0128] like Fig.18 As shown, at -1V, the multiplication type photodetector described in this embodiment obtains a high specific detection rate D * =3.3×10 13 Jones.

[0129] At 0.2 μW / cm 2 Under 980nm laser irradiation, the photodetector described in Comparative Example 1 has R=0.06A / W, EQE=7% and D * =1.3×10 11 Jones. The multiplication type photodetector described in Comparative Example 2 has R = 307A / W, EQE = 39019% and D * =2.4×10 13 Jones. The multiplication type photodetector described in Comparative Example 3 has R = 231A / W, EQE = 29305% and D * =1.1×10 13 Jones.

[0130] In order to verify the application of this multiplication type photodetector in the upconversion light-emitting device, the present invention prepared an ultra-sensitive upconversion light-emitting device of Comparative Examples 4-6 and Example 2 based on Comparative Examples 1-3 and Example 1. At the same time, the present invention tested the brightness of this upconversion light-emitting device under different voltages, such as Fig.19 Compared with Comparative Examples 4-6, Example 2 shows significantly higher brightness.

[0131] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for realizing a multiplication type photodetector, characterized in that: Prepare a metal top electrode, an infrared absorption layer, an electron transport layer 1, a transparent conductive bottom electrode and a glass substrate in order from top to bottom to obtain an amplification type photodetector; The electron transport layer is prepared by treating the ZnO thin film layer with a 2 wt % acetic acid-methanol solution, and then introducing interface oxygen vacancies into the ZnO thin film layer to form the electron transport layer.

2. A method for realizing a multiplication type photodetector as claimed in claim 1, characterized in that: The metal top electrode, the infrared absorption layer, the electron transport layer 1, the transparent conductive bottom electrode and the glass substrate are prepared in sequence from top to bottom to obtain an amplification type photodetector; The specific steps include: (1) synthesizing a ZnO material by a sol-gel method, and spin-coating the obtained ZnO material on a transparent conductive bottom electrode by an annealing recrystallization method to prepare an electron transport layer 1; the transparent conductive bottom electrode is fixed on a glass substrate; (2) spin coating a PbS colloidal quantum dot solution on the electron transport layer 1 to prepare an infrared absorption layer; (3) On the infrared absorption layer, a metal top electrode is prepared by using a mask and a thermal evaporation method to obtain an amplification type photodetector.

3. A method for realizing a multiplication type photodetector as claimed in claim 2, characterized in that: The infrared absorption layer is a narrow-bandgap semiconductor colloidal quantum dot material, the spin coating speed of the infrared absorption layer is 2000rpm-4000rpm, and the spin coating time is 30s-90s.

4. A method for realizing a multiplication type photodetector as claimed in claim 1, characterized in that: The preparation method of the ZnO thin film used as the electron transport layer is to synthesize a high-quality ZnO thin film layer by combining a sol-gel method and annealing recrystallization. The steps of the method are as follows: Zinc acetate dihydrate [Zn(Ac)2·2H2O] was mixed evenly in a solution of ethylene glycol methyl ether and ethanolamine with a volume ratio of 24:1, and then spin-coated onto an ITO glass substrate. The ITO glass substrate was then annealed at 300°C for 10 minutes, at which point Zn(Ac)2 was converted into ZnO. The surface of the ZnO film is cleaned by spin coating with an acetic acid-methanol solution, and the ZnO film is rinsed with isopropanol, acetone and ethanol, and finally dried at 200° C. for 10 minutes, at which time oxygen vacancies are introduced on the surface of the ZnO film layer.

5. A method for realizing a multiplication type photodetector as claimed in claim 4, characterized in that: The concentration of the zinc acetate dihydrate solution is 0.4M to 0.6M.

6. A method for realizing a multiplication type photodetector as claimed in any one of claims 1 to 5, characterized in that: The thickness of the metal top electrode is 30nm-150nm, the thickness of the electron transport layer 1 is 20nm-150nm, the thickness of the infrared absorption layer is 100nm-800nm, and the thickness of the transparent conductive bottom electrode is 50nm-180nm.

7. An up-conversion light-emitting device for realizing a multiplication-type photodetector, characterized in that: It includes a metal top electrode, an electrode modification layer, an electron transport layer 2, a light-emitting layer, a hole transport layer, an infrared absorption layer, an electron transport layer 1 and a transparent conductive bottom electrode prepared in sequence from top to bottom; wherein the electron transport layer 1 is a ZnO thin film layer with introduced interface oxygen vacancies as described in claim 1.

8. The up-conversion light-emitting device according to claim 7, characterized in that: The thickness of the electrode modification layer is 0.5nm-5nm, the thickness of the hole transport layer is 10nm-100nm, the thickness of the light-emitting layer is 30nm-100nm, the thickness of the electron transport layer 1 is 20nm-150nm, and the thickness of the electron transport layer 2 is 10nm-100nm.

9. The up-conversion light-emitting device according to claim 7, characterized in that: The hole transport layer in the organic light-emitting diode is 1-bis[4-[N,NN-di(4-methylphenyl)amino]phenyl]-cyclohexane (TAPC); Preferably, the light-emitting layer in the organic light-emitting diode is 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP) and tris(2-phenylpyridine)iridium [Ir(ppy)3]; Preferably, the weight ratio of the two materials in the CBP and Ir(ppy)3 mixture layer is 93:7; Preferably, the second electron transport layer in the organic light emitting diode is bathocuproin BCP; Preferably, the electrode modification layer in the organic light emitting diode is lithium fluoride LiF.

10. The up-conversion light-emitting device according to any one of claims 7 to 9, characterized in that: The metal top electrode is Al, and the transparent conductive bottom electrode is indium tin oxide ITO.

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