Multiplying type organic photoelectric detector based on hole blocking layer

Abstract

The invention discloses a multiplication type organic photoelectric detector based on a hole barrier layer. The detector comprises a cathode, an anode, a photosensitive layer arranged between the cathode and the anode, the hole barrier layer arranged between the anode and the photosensitive layer, and an electron transport layer arranged between the cathode and the photosensitive layer. Wherein the photosensitive layer comprises at least one donor material; the donor material with the lowest HOMO energy level in the photosensitive layer and the hole blocking layer meet the following relation: Hmin-HP is greater than or equal to 0.5 eV; the donor material with the highest HOMO energy level in the photosensitive layer and the hole blocking layer meet the following relation: LP-Hmax is greater than or equal to 2.0 eV; wherein Hmin represents the HOMO energy level of the donor material with the lowest HOMO energy level in the photosensitive layer, HP represents the HOMO energy level of the hole blocking layer, Hmax represents the HOMO energy level of the donor material with the highest HOMO energy level in the photosensitive layer, and LP represents the LUMO energy level of the hole blocking layer.

Description

Technical Field

[0001] The present invention relates to the technical field of optoelectronic devices, and more specifically, to an amplification-type organic photodetector based on a hole blocking layer. Background Art

[0002] A photodetector is a device that converts light signals into electrical signals and is widely used in health monitoring, optical communications, image sensing, industrial automation and other fields. Organic photodetectors have unique advantages in special applications and integration due to their light weight, low cost and flexibility. However, the external quantum efficiency of photodiode-type organic detectors is usually less than 100%, and the electrical signals generated under weak light conditions are weak, resulting in insufficient sensitivity in detecting weak light signals. Through the photomultiplier effect, organic photodetectors with an external quantum efficiency of more than 100% can detect weak light signals and have broad application prospects in fields such as bioimaging and long-distance optical communications.

[0003] In recent years, research on the multiplication mechanism of organic photodetectors has made some progress. The basic principle is to provide conditions for the generation of multiple carriers for each incident photon by confining the photogenerated carriers in a specific area. Common methods include the use of different donor-acceptor ratios, dopants, quantum dots and nanoparticles to capture carriers. However, these methods may introduce problems in device efficiency, stability, device structure configuration, etc. In addition, the multiplication-type organic photodetectors reported so far often require a higher operating voltage, which also puts forward higher requirements for the working conditions of the multiplication device, which is not conducive to low power consumption and highly integrated applications; and higher operating voltages will cause greater noise, resulting in a decrease in detector sensitivity. Therefore, there is an urgent need for a high-performance device that can not only ensure the stability of the intrinsic performance of the device but also achieve multiplication at a low bias voltage. Summary of the invention

[0004] The object of the present invention is to provide an amplification-type organic photodetector based on a hole blocking layer, so as to achieve amplification at a low bias voltage and ensure the stability of the intrinsic performance of the device.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A multiplication type organic photodetector based on a hole blocking layer, the detector comprising a cathode, an anode, a photosensitive layer arranged between the cathode and the anode, a hole blocking layer arranged between the anode and the photosensitive layer, and an electron transport layer arranged between the cathode and the photosensitive layer;

[0007] Wherein, the photosensitive layer comprises at least one donor material;

[0008] The donor material with the lowest HOMO energy level in the photosensitive layer and the hole blocking layer satisfy the following relationship:

[0009] H min -H P ≥0.5eV;

[0010] The donor material with the highest HOMO energy level in the photosensitive layer and the hole blocking layer satisfy the following relationship:

[0011] L P -H max ≥2.0eV;

[0012] Among them, H min represents the HOMO energy level of the donor material with the lowest HOMO energy level in the photosensitive layer, H P represents the HOMO energy level of the hole blocking layer, H max represents the HOMO energy level of the donor material with the highest HOMO energy level in the photosensitive layer, L P represents the LUMO level of the hole blocking layer.

[0013] Preferably, the material of the hole blocking layer includes but is not limited to one of BCP, PFN-Br and BPhen.

[0014] Preferably, the donor material includes but is not limited to PTB7-Th or P3HT.

[0015] Preferably, the photosensitive layer further comprises at least one receptor material, the receptor material includes but is not limited to: IEICO-4F, DPA-4F or PC 61 BM.

[0016] Furthermore, the thickness of the hole blocking layer is regulated between 6 nm and 30 nm.

[0017] Preferably, the material of the electron transport layer is selected from organic compounds, inorganic compounds, or a combination thereof;

[0018] Wherein, the organic compound is selected from fullerene and its derivatives, 4,7-diphenyl-1,10-phenanthroline, polyethyleneimine, polyethoxyethyleneimine, 2,9-dimethyl-4,7-biphenyl-1,10-phenanthroline,

[0019] [9,9-dioctylfluorene-9,9-bis(N,N-dimethylaminopropyl)fluorene], bromo-[9,9-dioctylfluorene-9,9-bis(N,N-dimethylaminopropyl)fluorene], 8-hydroxyquinoline lithium, 1,3,5-tri(1-phenyl-1H-benzimidazol-2-yl)benzene, bis(2-methyl-8-quinolinol)-4-(phenylphenol)aluminum, 1,3,5-tri[(3-pyridyl)-phenyl-3-yl]benzene, or a mixture or a composite of the above materials;

[0020] The inorganic compound is selected from zinc oxide, tin oxide, aluminum-doped zinc oxide, magnesium-doped zinc oxide, gallium-doped zinc oxide, titanium oxide, tantalum oxide, zinc sulfide, chromium sulfide, or a mixture or composite of the above materials.

[0021] Furthermore, the thickness of the electron transport layer is regulated between 8nm and 50nm.

[0022] Preferably, at least one of the anode and the cathode is configured to be transparent or semi-transparent.

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

[0024] In the multiplication type organic photodetector described in the present invention, the role of the hole blocking layer is to achieve effective accumulation of photogenerated holes, resulting in band bending of the hole blocking layer, thereby achieving a large amount of electron injection under a relatively low external bias voltage, so that the multiplication type organic photodetector described in the present invention achieves photomultiplication. To this end, the hole blocking layer and the electron transport layer have a deeper HOMO energy level relative to the photosensitive layer, and when the forward bias and reverse bias are applied, the holes are accumulated at the interface to cause band bending, induce electron tunneling injection, and produce a bidirectional photomultiplication effect, thereby realizing a device with low operating voltage, high external quantum efficiency and high specific detection rate.

[0025] The present invention introduces a hole blocking layer without affecting the intrinsic proportion and composition of the photosensitive layer. The structure is suitable for different photosensitive layer materials and has wide applicability.

[0026] The multiplication type organic photodetector of the present invention can show excellent multiplication effect at low working voltage, and can realize the multiplication effect of bidirectional injection at the lowest ±0.2 V. The multiplication type organic photodetector of the present invention has a simple structure and is easy to prepare. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic structural diagram of the multiplication type organic photodetector of the present invention.

[0028] Figure 2 It is a schematic diagram of the energy levels of the materials involved in the present invention.

[0029] Figure 3 It is a schematic diagram of the working mechanism of the multiplication-type organic photodetector of the present invention.

[0030] Figure 4 This is a graph of the external quantum efficiency of an organic photodetector with BCP as a hole blocking layer under a bias voltage of ±2V provided in Example 1 of the present invention.

[0031] Figure 5This is a graph of the external quantum efficiency of an organic photodetector with PFN-Br as a hole blocking layer under a bias voltage of ±2V provided in Example 1 of the present invention.

[0032] Figure 6 This is a graph of the external quantum efficiency of an organic photodetector using BPhen as a hole blocking layer under a bias voltage of ±2V provided in Example 1 of the present invention.

[0033] Figure 7 This is a current-voltage curve diagram of the organic photodetector based on the three hole blocking layers provided in Example 1 of the present invention in the dark state at a bias voltage of -2V to 2V.

[0034] Figure 8 This is a curve diagram of the specific detection rate of the organic photodetector based on the three hole blocking layers provided in Example 1 of the present invention at a bias voltage of -2V.

[0035] Fig. 9 This is a graph of the external quantum efficiency of an organic photodetector with BCP as a hole blocking layer under a bias voltage of -2V to -0.5V provided in Example 1 of the present invention.

[0036] Fig.10 This is a graph of the external quantum efficiency of an organic photodetector with BCP as a hole blocking layer under a bias voltage of ±2V provided in Example 2 of the present invention.

[0037] Fig.11 This is a graph of the external quantum efficiency of an organic photodetector with PFN-Br as a hole blocking layer under a bias voltage of ±2V provided in Example 2 of the present invention.

[0038] Fig.12 This is a graph of the external quantum efficiency of an organic photodetector using BPhen as a hole blocking layer under a bias voltage of ±2V provided in Example 2 of the present invention.

[0039] Fig.13 This is a current-voltage curve diagram of the organic photodetector based on the three hole blocking layers provided in Example 2 of the present invention in the dark state at a bias voltage of -2V to 2V.

[0040] Fig.14 This is a curve diagram of the specific detection rate of the organic photodetector based on the three hole blocking layers provided in Example 2 of the present invention at a bias voltage of -2V.

[0041] Fig.15 This is a graph of the external quantum efficiency of an organic photodetector with BCP as a hole blocking layer under a bias voltage of ±0.2V provided in Example 3 of the present invention.

[0042] Fig.16This is a graph of the external quantum efficiency of an organic photodetector with PFN-Br as a hole blocking layer under a bias voltage of ±0.2V provided in Example 3 of the present invention.

[0043] Fig.17 This is a graph of the external quantum efficiency of an organic photodetector using BPhen as a hole blocking layer under a bias voltage of ±0.2 V provided in Example 3 of the present invention. DETAILED DESCRIPTION

[0044] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. The present invention is described in detail below in combination with the drawings and specific implementation methods.

[0045] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0046] It should also be understood that the terms used in this specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the specification of the present invention and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0047] It should be further understood that the term "and / or" used in the present description and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0048] In order to realize a high-performance device that can ensure the stability of the intrinsic performance of the device and can achieve multiplication under low bias voltage. Figure 1 As shown, the present invention provides an amplification type organic photodetector based on a hole blocking layer, the detector comprising a cathode, an anode, a photosensitive layer arranged between the cathode and the anode, a hole blocking layer arranged between the anode and the photosensitive layer, and an electron transport layer arranged between the cathode and the photosensitive layer;

[0049] Wherein, the photosensitive layer comprises at least one donor material;

[0050] The donor material with the lowest HOMO energy level in the photosensitive layer and the hole blocking layer satisfy the following relationship:

[0051] H min -H P ≥0.5eV;

[0052] The donor material with the highest HOMO energy level in the photosensitive layer and the hole blocking layer satisfy the following relationship:

[0053] L P -H max ≥2.0eV;

[0054] Among them, H min represents the HOMO energy level of the donor material with the lowest HOMO energy level in the photosensitive layer, H P represents the HOMO energy level of the hole blocking layer, H max represents the HOMO energy level of the donor material with the highest HOMO energy level in the photosensitive layer, L P represents the LUMO level of the hole blocking layer.

[0055] When the multiplication type organic photodetector described in the present invention is illuminated, photons are absorbed by the photosensitive layer, excitons are generated in the photosensitive layer, and then the excitons dissociate at the donor-acceptor interface in the photosensitive layer to form free charges. Under forward bias, since the hole transport layer HBL has a high potential barrier, photogenerated holes accumulate at the interface of the photosensitive layer BHJ-HBL, causing the energy band of BHJ to bend. Considering that the thickness of HBL is relatively thin, holes can achieve tunneling under the action of an external bias, thereby generating gain. Under reverse bias, similar to forward bias, photogenerated holes accumulate at the interface of BHJ-electron transport layer, resulting in energy band bending, thereby reducing the electron injection barrier. Electrons injected under external bias increase the photocurrent, achieve PM, and supplement the hole resistance. The multiplication type organic photodetector described in the present invention can achieve an external quantum efficiency greater than 100% under both forward and reverse bias, and the weak light photoresponse is significantly higher than that of ordinary photodetectors.

[0056] It should be noted that the hole transport layer of the present invention is a single-layer structure, and there is no need to set up multiple hole transport layers to form traps, thereby simplifying the device structure.

[0057] In addition, the present invention also requires that the difference between the LUMO energy level of the hole blocking layer and the HOMO energy level of the donor material with the highest HOMO energy level in the photosensitive layer is greater than or equal to 2.0. This energy level difference can effectively inhibit non-radiative recombination, thereby extending the life of the blocked holes and further improving the gain effect.

[0058] Preferably, the material of the hole blocking layer includes but is not limited to one of BCP, PFN-Br and BPhen.

[0059] Preferably, the donor material includes but is not limited to PTB7-Th or P3HT.

[0060] Preferably, the photosensitive layer further comprises at least one receptor material, the receptor material includes but is not limited to: IEICO-4F, DPA-4F or PC 61 BM.

[0061] The materials, donor materials, and acceptor materials of the hole transport layer are only a few of those listed in the present invention. As long as the materials and donor materials of the hole transport layer can satisfy the above relationship, they all belong to the protection scope of the present invention. As for the donor material, it can be selected according to the actual working band required by the photosensitive layer and used in combination with the donor material.

[0062] Preferably, the thickness of the hole blocking layer is regulated between 6 nm and 30 nm. On the one hand, the thickness of the hole blocking layer cannot be too thin to ensure good film forming properties. On the other hand, the hole blocking layer cannot be too thick to ensure that the accumulated photogenerated holes can cause the energy band bending of the hole blocking layer, and finally can be injected through the hole blocking layer to produce a photomultiplier effect.

[0063] In the present invention, the light response range of the photosensitive layer is 300 to 1400 nm. The combination of the donor material and the acceptor material in the photosensitive layer can be: PTB7-Th:IEICO-4F, PTB7-Th:DPA-4F or P3HT:PC 61 BM.

[0064] In the present invention, the photosensitive layer may adopt a planar heterojunction or a bulk heterojunction; preferably, the photosensitive layer of the present invention adopts a bulk heterojunction structure formed by a donor material and an acceptor material.

[0065] In the present invention, the combination of the donor material in the photosensitive layer and the hole blocking layer can be: PTB7-Th:BCP, PTB7-Th:PFN-Br, PTB7-Th:BPhen, P3HT:BCP, P3HT:PFN-Br, P3HT:BPhen.

[0066] Preferably, the material of the electron transport layer is selected from organic compounds, inorganic compounds, or a combination thereof;

[0067] Wherein, the organic compound is selected from fullerene and its derivatives, 4,7-diphenyl-1,10-phenanthroline, polyethyleneimine, polyethoxyethyleneimine, 2,9-dimethyl-4,7-biphenyl-1,10-phenanthroline, [9,9-dioctylfluorene-9,9-bis(N,N-dimethylaminopropyl)fluorene], bromo-[9,9-dioctylfluorene-9,9-bis(N,N-dimethylaminopropyl)fluorene], 8-hydroxyquinoline lithium, 1,3,5-tri(1-phenyl-1H-benzimidazol-2-yl)benzene, bis(2-methyl-8-quinolinol)-4-(phenylphenol)aluminum, 1,3,5-tri[(3-pyridyl)-phenyl-3-yl]benzene, or a mixture or a composite of the above materials;

[0068] The inorganic compound is selected from zinc oxide, tin oxide, aluminum-doped zinc oxide, magnesium-doped zinc oxide, gallium-doped zinc oxide, titanium oxide, tantalum oxide, zinc sulfide, chromium sulfide, or a mixture or composite of the above materials.

[0069] Preferably, the thickness of the electron transport layer is regulated between 8 nm and 50 nm.

[0070] Preferably, at least one of the anode and the cathode is configured to be transparent or semi-transparent.

[0071] If we list examples of the constituent materials of the electrodes (anode, cathode), we can cite: metals such as platinum, gold, silver, aluminum, chromium, nickel, copper, titanium, magnesium, calcium, barium, sodium, or their alloys; metal oxides such as indium oxide and tin oxide, or their composite oxides (such as ITO, IZO); conductive polymers such as polyaniline, polypyrrole, polythiophene, polyacetylene, etc.; those obtained by adding acids such as hydrochloric acid, sulfuric acid, sulfonic acid, Lewis acids such as FeCl3, halogen atoms such as iodine, metal atoms such as sodium, potassium, etc. to the above conductive polymers; conductive composite materials in which conductive particles such as metal particles, carbon black, fullerene, carbon nanotubes, etc. are dispersed in a matrix such as a polymer binder, etc. The constituent materials of the electrodes can be used alone or in combination of two or more in any combination and ratio.

[0072] Generally, examples of materials constituting transparent or translucent electrodes include any single substance of titanium (Ti), tungsten (W), titanium nitride (TiN), platinum (Pt), gold (Au), germanium (Ge), nickel (Ni) and aluminum (Al), and alloys containing at least one of them. Among them, in particular, indium titanium oxide (ITiO) has high light transmittance relative to the infrared region, and is expected to be used as a constituent material of a transparent electrode. In addition to the above-mentioned materials, examples of materials for transparent or translucent electrodes also include indium tin oxide (ITO), tin (Sn), tin oxide (SnO2), IWO, indium zinc composite oxide (IZO), zinc-doped aluminum oxide (AZO), zinc-doped gallium oxide (GZO), aluminum oxide doped with magnesium and zinc (AlMgZnO), indium gallium composite oxide (IGO), In-GaZnO4 (IGZO), fluorine-doped indium oxide (IFO), antimony-doped tin oxide (ATO), fluorine-doped tin oxide (FTO), zinc oxide (ZnO), boron-doped ZnO, and InSnZnO.

[0073] Wherein, the preparation of the photosensitive layer is selected from solution film formation or vacuum thermal evaporation deposition method.

[0074] The preparation of the electron transport layer and the hole blocking layer are independently selected from one or more of solution film formation, sol-gel film formation, vacuum thermal evaporation, atomic layer deposition, chemical vapor deposition, electrodeposition, and anodization.

[0075] The cathode and the anode are prepared independently by one or more methods selected from vacuum thermal evaporation, electron beam evaporation, molecular beam evaporation or plasma sputtering, atomic layer deposition or liquid film formation followed by reduction conversion, electroplating or electrodeposition.

[0076] The multiplication type organic photodetector can adopt an inverted structure or a face-up structure; wherein,

[0077] The inverted structure includes, from bottom to top, a substrate, a cathode close to the substrate, an electron transport layer, a photosensitive layer, a hole blocking layer, and an anode.

[0078] The upright structure includes, from bottom to top, a substrate, an anode close to the substrate, a hole blocking layer, a photosensitive layer, an electron transport layer, a cathode, and an encapsulation layer.

[0079] Generally, the multiplication type organic photodetector further comprises an encapsulation layer for encapsulation. The preparation of the encapsulation layer is selected from one of vacuum thermal evaporation, chemical vapor deposition, atomic layer deposition, plasma sputtering, and liquid film formation.

[0080] Commonly used inorganic packaging materials include silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, zirconium oxide, magnesium oxide, zirconium oxide and magnesium fluoride. Commonly used organic packaging materials include polymethyl methacrylate, polyethylene oxide, polystyrene, polyvinyl pyrrolidone, polycarbonate, polyacrylic acid, epoxy resin, polyparaxylene and polysiloxazane.

[0081] Example 1

[0082] In this embodiment, a multiplication type organic photodetector based on a hole blocking layer is provided, and its structure is as follows: Figure 1 As shown, from bottom to top are a glass substrate, a translucent cathode (ITO, 150 nm thick), an electron transport layer (zinc oxide (ZnO), 30 nm thick), a photosensitive layer, a hole blocking layer, and an anode (silver, 100 nm thick).

[0083] The photosensitive layer is formed by blending a donor material of PTB7-Th and an acceptor material of IEICO-4F to form a bulk heterojunction; the mass ratio of the donor and acceptor materials is 1:1.5, the concentration is 25 mg / ml, and the thickness is 230 nm. The hole blocking layer is one of BCP, PFN-Br or BPhen, and the thickness is 6 nm, 8 nm or 10 nm respectively. The energy level diagram of the hole blocking layer and the donor material is as follows: Figure 2 shown.

[0084] The difference between the HOMO energy level of the donor material PTB7-Th and the HOMO energy level of BCP is 1.21 eV.

[0085] The difference between the HOMO energy level of the donor material PTB7-Th and the LUMO energy level of BCP is 2.29 eV.

[0086] The difference between the HOMO energy level of the donor material PTB7-Th and the HOMO energy level of PFN-Br is 0.51 eV.

[0087] The difference between the HOMO energy level of the donor material PTB7-Th and the LUMO energy level of PFN-Br is 2.39 eV.

[0088] The difference between the HOMO energy level of the donor material PTB7-Th and the HOMO energy level of BPhen is 1.27 eV.

[0089] The difference between the HOMO energy level of the donor material PTB7-Th and the LUMO energy level of BPhen is 2.19 eV.

[0090] Therefore, it can be seen that the energy levels of the donor material and the hole blocking layer satisfy the following relationship:

[0091] The donor material with the lowest HOMO energy level in the photosensitive layer and the hole blocking layer satisfy the following relationship:

[0092] H min -H P ≥0.5eV;

[0093] The donor material with the highest HOMO energy level in the photosensitive layer and the hole blocking layer satisfy the following relationship:

[0094] L P -H max ≥2.19eV.

[0095] The preparation method of the organic photodetector based on the hole blocking layer in this example is as follows:

[0096] S1. First, use acetone to ultrasonically clean the glass substrate with ITO for 10 to 15 minutes, then use deionized water and detergent to ultrasonically clean it for 10 to 15 minutes, then repeat the ultrasonic cleaning with deionized water three times, and finally use acetone to ultrasonically clean it again for 10 to 15 minutes, and put it in an oven to dry for later use.

[0097] S2. Perform oxygen plasma treatment on the glass substrate with ITO for 60 to 90 seconds.

[0098] S3. Filter the ZnO solution prepared by the sol-gel method with a hydrophobic needle, and then spin-coat it onto the ITO glass substrate treated by S2 at a spin-coating speed of 3300 rpm for 40 s. Anneal on a hot plate at 100°C for 30 min to obtain an electron transport layer.

[0099] S4, spin-coat the prepared 25 mg / mL photosensitive layer solution (the solvent is chlorobenzene, and 2% chloronaphthalene additive is added) on the electron transport layer obtained in S3. The spin coating process is step-by-step spin coating, first at 800 rpm for 40 seconds, and then at 2000 rpm for 20 seconds. Immediately after spin coating, transfer the sample to a vacuum chamber and evacuate for at least 2 hours. After evacuation, transfer the sample to a 100°C hot stage for annealing for 10 minutes.

[0100] S5. This example uses three different hole blocking layers:

[0101] BCP: Spin-coat the prepared BCP saturated solution (solvent is isopropyl ketone) on the sample obtained in S4 at a spin-coating speed of 4000 rpm for 30 s to obtain a hole blocking layer.

[0102] PFN-Br: Spin-coat the prepared 0.5 mg / mL PFN-Br solution (the solvent is methanol) on the sample obtained in S4 at a spin-coating speed of 2000 rpm for 60 s to obtain a hole blocking layer.

[0103] BPhen: The sample obtained in S4 was transferred to a vacuum evaporation system, and a BPhen hole blocking layer was evaporated on the photosensitive layer.

[0104] S6. Transfer the above samples to a vacuum evaporation system, evaporate a layer of metallic silver on the hole blocking layer as an anode, and finally prepare multiplication type photodetectors with structures of ITO / ZnO / PTB7-Th:IEICO-4F / BCP / Ag, ITO / ZnO / PTB7-Th:IEICO-4F / PFN-Br / Ag, and ITO / ZnO / PTB7-Th:IEICO-4F / BPhen / Ag.

[0105] In the present invention, if Figure 3 As shown, under dark conditions, the multiplication type organic photodetector described in the present invention is blocked from carrier transport under the action of the hole transport layer HBL at zero bias, and there is no light response. When the multiplication type organic photodetector described in the present invention is illuminated, photons are absorbed by the photosensitive layer, excitons are generated at the PTB7-TH and IEICO-4F bulk heterojunction interface, and then the excitons dissociate at the donor-acceptor interface to form free charges. Under forward bias, since the hole transport layer HBL has a high potential barrier, photogenerated holes accumulate at the BHJ-HBL interface, causing the energy band of BHJ to bend. Considering that the thickness of HBL is relatively thin, holes can achieve tunneling under the action of an external bias, thereby generating gain. Under reverse bias, similar to forward bias, photogenerated holes accumulate at the BHJ-ZnO interface, resulting in energy band bending, thereby reducing the electron injection barrier. Under external bias, electrons are injected to increase the photocurrent, achieve PM, and supplement the hole resistance. Since the thickness of ZnO is slightly higher than that of HBL, its hole tunneling is slightly more difficult than that under forward bias, resulting in the EQE after gain being slightly lower than that under forward bias. In summary, the amplified organic photodetector described in the present invention can achieve an external quantum efficiency greater than 100% under both forward and reverse bias, and its weak light photoresponse is significantly higher than that of ordinary photodetectors.

[0106] Figures 4 to 6 The external quantum efficiency curve of the multiplication type organic photodetector involved in this example under ±2V bias is given. It can be seen from the figure that the multiplication type organic photodetector based on the three selected hole blocking layers in this example all show an external quantum efficiency far exceeding 100% in the range of 300nm to 1100nm, and the maximum external quantum efficiency exceeds 100000%. It should also be pointed out that the photodetector described in the present invention has bidirectional multiplication, and under ±2V bias, its multiplication effect is basically the same. Figure 7 As shown, the current density-voltage curves of the dark state of the multiplication-type organic photodetector based on three blocking layers. Figure 8The specific detection rate diagram of the multiplication type organic photodetector involved in this example under -2V bias voltage is given. The detector specific detection rate corresponding to the three blocking layers reaches up to 10 13 The highest level is more than 5×10 13 Jones.

[0107] The multiplication-type organic photodetector of the present invention can show excellent multiplication effect at a low operating voltage. Fig. 9 As shown, the bidirectional injection multiplication effect can be achieved at a minimum of -0.5 V. The multiplication type organic photodetector of the present invention has a simple structure and is easy to prepare.

[0108] Example 2

[0109] The multiplication type organic photodetector based on the hole blocking layer provided in this embodiment is as follows: Figure 1 As shown, its structure from bottom to top is a glass substrate, a semi-transparent conductive cathode (ITO, 150nm), an electron transport layer (ZnO, 30nm thick), a photosensitive layer, a hole blocking layer (one of BCP, PFN-Br or BPhen, with thickness of 6nm, 8nm or 10nm respectively), and an anode (silver, 100nm thick).

[0110] The photosensitive layer is a bulk heterojunction formed by blending a donor material of PTB7-Th and an acceptor material of DPA-4F; the donor-acceptor mass ratio is 1:1.5, the concentration is 25 mg / ml, and the thickness of the photosensitive layer is 240 nm. The preparation method of the organic photodetector based on the hole blocking layer in this example is as follows:

[0111] S1. First, ultrasonically clean the glass substrate with acetone for 10 to 15 minutes, then ultrasonically clean it with deionized water and detergent for 10 to 15 minutes, then repeat the ultrasonic cleaning with deionized water three times, and finally ultrasonically clean it again with acetone for 10 to 15 minutes, and put it in an oven to dry for later use.

[0112] S2. Perform oxygen plasma treatment on the glass substrate with ITO for 60 to 90 seconds.

[0113] S3. Filter the ZnO solution prepared by the sol-gel method with a hydrophobic needle, and then spin-coat it onto the ITO glass substrate treated by S2 at a spin-coating speed of 3300 rpm for 40 s. Anneal on a hot plate at 100°C for 30 min to obtain an electron transport layer.

[0114] S4, spin-coat the prepared 25 mg / mL photosensitive layer solution (the solvent is chlorobenzene, and 2% chloronaphthalene additive is added) on the ZnO layer obtained in S3. The spin coating process is step-by-step spin coating, first at 800 rpm for 40 seconds, and then at 2000 rpm for 20 seconds. Immediately after spin coating, transfer the sample to a vacuum chamber and evacuate for at least 2 hours. After evacuation, transfer the sample to a 100°C hot stage for annealing for 10 minutes.

[0115] S5. This example uses three different hole blocking layers:

[0116] BCP: A saturated solution of BCP, with isopropyl ketone as the solvent, was spin-coated on the sample obtained in S4 at a spin-coating speed of 4000 rpm for 30 s to obtain a hole blocking layer.

[0117] PFN-Br: A PFN-Br solution with a concentration of 0.5 mg / mL and a solvent of methanol was spin-coated on the sample obtained in S4 at a spin-coating speed of 2000 rpm for 60 s to obtain a hole blocking layer.

[0118] BPhen: The sample obtained in S4 was transferred to a vacuum evaporation system, and a BPhen hole blocking layer was evaporated on the photosensitive layer.

[0119] S6. Transfer the above samples to a vacuum evaporation system, evaporate a metal silver electrode on the hole blocking layer, and finally prepare multiplication type photodetectors with the structures of ITO / ZnO / PTB7-Th:DPA-4F / BCP / Ag, ITO / ZnO / PTB7-Th:DPA-4F / PFN-Br / Ag, and ITO / ZnO / PTB7-Th:DPA-4F / BPhen / Ag.

[0120] Figure 10 to Figure 12 The external quantum efficiency curve of the amplified organic photodetector involved in this example under ±2V bias is given. It can be seen from the figure that the amplified organic photodetectors based on the three selected hole blocking layers in this example all show an external quantum efficiency far exceeding 100% in the range of 300nm to 1200nm, and the maximum external quantum efficiency exceeds 10000%. Fig.13 This is the current density-voltage curve in the dark state of the multiplication-type organic photodetector based on three blocking layers. Fig.14 The specific detection rate diagram of the multiplication type organic photodetector involved in this example under -2V bias voltage is given. The detector specific detection rate corresponding to the three blocking layers reaches up to 10 12 The highest level is more than 5×10 12 Jones.

[0121] Example 3

[0122] The multiplication type organic photodetector based on the hole blocking layer provided in this embodiment is as follows: Figure 1 As shown, its structure from bottom to top is a semi-transparent and conductive cathode (ITO, 150nm), an electron transport layer (ZnO, thickness 30nm), a photosensitive layer, a hole blocking layer (one of BCP, PFN-Br or BPhen, with thickness of 6nm, 8nm or 10nm respectively), and an anode (silver, thickness of 100nm); the donor material in the photosensitive layer is P3HT, and the acceptor material is PC 61 BM, donor-acceptor mass ratio was 1:1, concentration was 10 mg / ml, and thickness was 70 nm.

[0123] The difference between the HOMO energy level of the donor material P3HT and the HOMO energy level of BCP is 1.4 eV.

[0124] The difference between the HOMO energy level of the donor material P3HT and the LUMO energy level of BCP is 2.1 eV.

[0125] The difference between the HOMO energy level of the donor material P3HT and the HOMO energy level of PFN-Br is 0.7 eV.

[0126] The difference between the HOMO energy level of the donor material P3HT and the LUMO energy level of PFN-Br is 2.2 eV.

[0127] The difference between the HOMO energy level of the donor material P3HT and the HOMO energy level of BPhen is 1.46 eV.

[0128] The difference between the HOMO energy level of the donor material P3HT and the LUMO energy level of BPhen is 2.0 eV.

[0129] The preparation method of the organic photodetector based on the hole blocking layer in this example is as follows:

[0130] S1. First, ultrasonically clean the glass substrate with acetone for 10 to 15 minutes, then ultrasonically clean it with deionized water and detergent for 10 to 15 minutes, then repeat the ultrasonic cleaning with deionized water three times, and finally ultrasonically clean it again with acetone for 10 to 15 minutes, and put it in an oven to dry for later use.

[0131] S2. Perform oxygen plasma treatment on the glass substrate with ITO for 60 to 90 seconds.

[0132] S3. Filter the ZnO solution prepared by the sol-gel method with a hydrophobic needle, and then spin-coat it onto the ITO glass substrate treated by S2 at a spin-coating speed of 3300 rpm for 40 s. Anneal on a hot plate at 100°C for 30 min to obtain an electron transport layer.

[0133] S4. Spin-coat a photosensitive layer solution with a concentration of 14 mg / mL and a solvent of chlorobenzene on the ZnO layer obtained in S3 at a spin-coating speed of 2000 rpm for 40 seconds. After spin coating, immediately transfer the sample to a hot plate at 100°C for annealing for 10 minutes.

[0134] S5. This example uses three different hole blocking layers:

[0135] BCP: A saturated solution of BCP, with isopropyl ketone as the solvent, was spin-coated on the sample obtained in S4 at a spin-coating speed of 4000 rpm for 30 s to obtain a hole blocking layer.

[0136] PFN-Br: A PFN-Br solution with a concentration of 0.5 mg / mL and a solvent of methanol was spin-coated on the sample obtained in S4 at a spin-coating speed of 2000 rpm for 60 s to obtain a hole blocking layer.

[0137] BPhen: The sample obtained in S4 was transferred to a vacuum evaporation system, and a BPhen hole blocking layer was evaporated on the photosensitive layer.

[0138] S6. The sample was transferred to a vacuum evaporation system, and a metal silver electrode was evaporated on the hole blocking layer to finally prepare a structure of ITO / ZnO / P3HT:PC 61 BM / BCP / Ag, ITO / ZnO / P3HT:PC 61 BM / PFN-Br / Ag、ITO / ZnO / P3HT:PC 61 BM / BPhen / Ag multiplication type photodetector.

[0139] Figure 15 to Figure 17 The external quantum efficiency curve of the amplified organic photodetector involved in this example under a bias voltage of ±0.2 V is given. As can be seen from the figure, the amplified organic photodetectors based on the two selected hole blocking layers in this example all show an external quantum efficiency of more than 100% within the range of 700 nm, with an obvious weak gain effect.

[0140] According to the above embodiments, by inserting a hole blocking layer between the photosensitive layer and the anode, the effective accumulation of photogenerated holes is achieved, resulting in band bending, and a large amount of electron injection is achieved under a relatively low external bias voltage, so that the multiplication type organic photodetector of the present invention can achieve photomultiplication. Under a bias voltage of ±2, the external quantum efficiency of the multiplication type organic photodetector at a wavelength of 820nm can reach 8018%, and the specific detection rate can reach 1.02×10 13Jones. The multiplication-type organic photodetector of the present invention has stable performance and good universality. Under the condition that the energy level requirements between the photosensitive layer and the hole blocking layer of the present invention are met, it can show excellent multiplication effect under bidirectional bias voltages as low as -2V and 2V. The present invention provides a bidirectionally biased multiplication-type organic photodetector that maintains high gain while reducing power consumption, and is suitable for a variety of application scenarios.

[0141] Obviously, the above embodiments of the present invention are only examples for clearly explaining the present invention, and are not intended to limit the implementation methods of the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A multiplication type organic photodetector based on a hole blocking layer, characterized in that: The detector comprises a cathode, an anode, a photosensitive layer arranged between the cathode and the anode, a hole blocking layer arranged between the anode and the photosensitive layer, and an electron transport layer arranged between the cathode and the photosensitive layer; Wherein, the photosensitive layer comprises at least one donor material; The donor material with the lowest HOMO energy level in the photosensitive layer and the hole blocking layer satisfy the following relationship: H min -H P ≥0.5eV; The donor material with the highest HOMO energy level in the photosensitive layer and the hole blocking layer satisfy the following relationship: H P -H max ≥2.0eV; Among them, H min represents the HOMO energy level of the donor material with the lowest HOMO energy level in the photosensitive layer, H P represents the HOMO energy level of the hole blocking layer, H max represents the HOMO energy level of the donor material with the highest HOMO energy level in the photosensitive layer, L P represents the LUMO level of the hole blocking layer.

2. The multiplication type organic photodetector based on a hole blocking layer according to claim 1, characterized in that: The material of the hole blocking layer includes but is not limited to one of BCP, PFN-Br, and BPhen.

3. The multiplication type organic photodetector based on a hole blocking layer according to claim 1, characterized in that: The donor material includes but is not limited to PTB7-Th or P3HT.

4. The multiplication type organic photodetector based on a hole blocking layer according to claim 1, characterized in that: The photosensitive layer further comprises at least one receptor material, including but not limited to: IEICO-4F, DPA-4F or PC 61 BM.

5. The multiplication type organic photodetector based on a hole blocking layer according to claim 3, characterized in that: The thickness of the hole blocking layer is adjusted between 6 nm and 30 nm.

6. The multiplication type organic photodetector based on a hole blocking layer according to claim 1, characterized in that: The material of the electron transport layer is selected from organic compounds, inorganic compounds, or a combination thereof; Wherein, the organic compound is selected from fullerene and its derivatives, 4,7-diphenyl-1,10-phenanthroline, polyethyleneimine, polyethoxyethyleneimine, 2,9-dimethyl-4,7-biphenyl-1,10-phenanthroline, [9,9-dioctylfluorene-9,9-bis(N,N-dimethylaminopropyl)fluorene], bromo-[9,9-dioctylfluorene-9,9-bis(N,N-dimethylaminopropyl)fluorene], 8-hydroxyquinoline lithium, 1,3,5-tri(1-phenyl-1H-benzimidazol-2-yl)benzene, bis(2-methyl-8-quinolinol)-4-(phenylphenol)aluminum, 1,3,5-tri[(3-pyridyl)-phenyl-3-yl]benzene, or a mixture or a composite of the above materials; The inorganic compound is selected from zinc oxide, tin oxide, aluminum-doped zinc oxide, magnesium-doped zinc oxide, gallium-doped zinc oxide, titanium oxide, tantalum oxide, zinc sulfide, chromium sulfide, or a mixture or composite of the above materials.

7. The multiplication type organic photodetector based on a hole blocking layer according to claim 6, characterized in that: The thickness of the electron transport layer is regulated between 8 nm and 50 nm.

8. The multiplication type organic photodetector based on a hole blocking layer according to claim 1, characterized in that: At least one of the anode and the cathode is configured to be transparent or semi-transparent.

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