A narrow-band organic photodetector and a method of manufacturing the same

Abstract

This invention discloses a narrow-band organic photodetector and its fabrication method. The structure of the narrow-band organic photodetector includes a glass substrate, a conductive anode layer, a hole selection layer, an organic material blend layer, an electron selection layer, and a metal electrode layer. The organic material blend layer is fabricated using a two-layer sequential deposition method, consisting of a blend of P-type and N-type materials. The two types of materials are spatially distributed in a vertical gradient, enabling the device to simultaneously achieve effective exciton separation and effective blocking of reverse electrons and holes. Compared with existing traditional thick heterojunction devices, it exhibits higher quantum efficiency and lower noise current. This invention, by controlling the organic material blend layer, achieves narrow-band optical detection functionality with a novel device structure and simple fabrication process, without the need for external filters or pre-layers. It exhibits particularly accurate and efficient detection capabilities in the near-infrared region, showing significant application potential.

Description

Technical Field

[0001] This invention relates to the field of optical detection technology, and in particular to a narrow-band organic photodetector and its fabrication method. Background Technology

[0002] A photodetector is a semiconductor device that uses the photoelectric effect to convert light signals into electrical signals. It can be used in many fields such as imaging systems, medical sensing, environmental monitoring, and optical communication.

[0003] Organic semiconductor materials have advantages such as wide availability, tunable molecular structure, ease of large-area fabrication, and flexibility, making them a promising candidate for photodetector applications.

[0004] To meet the needs of practical applications, organic molecules are designed as photoactive materials with different spectral responses to achieve precise and efficient photodetection performance.

[0005] Broadband organic photodetectors typically have photoelectric response across the entire ultraviolet-visible-infrared band, but they are susceptible to interference from ambient background light when a specific wavelength of light needs to be detected. Therefore, there is an urgent need to develop organic photodetectors with narrowband spectral response.

[0006] Currently, the main methods for fabricating and working principles of narrow-band organic photodetectors reported in the literature are as follows:

[0007] One approach is to use narrowband-absorbing photosensitive materials as photoactive layers to fabricate narrowband-responsive detectors.

[0008] Second, by utilizing intramolecular charge transfer, the device structure can be modulated to obtain narrowband absorption in singlet states;

[0009] Third, charge collection narrowing is used to prepare ultra-thick active film, which absorbs light only from the material band edge to obtain narrow-band response.

[0010] In addition, there are attempts to use complex device structures or fabricate optical microcavities to achieve narrowband detection capabilities.

[0011] However, the above strategies have drawbacks such as limited material selection, weak absorption, or complex fabrication processes. In addition, the difficulty in separating near-infrared excitons leads to low external quantum efficiency. Therefore, researching and inventing efficient narrow-band organic optoelectronic devices is a challenge in this field and is of great significance. Summary of the Invention

[0012] The purpose of this invention is to overcome the shortcomings and deficiencies of the prior art and to provide a narrow-band organic photodetector and its fabrication method.

[0013] This invention is achieved through the following technical solution:

[0014] A narrow-band organic photodetector has a structure comprising, from bottom to top, a glass substrate, a conductive anode layer, a hole selection layer, an organic material blend layer, an electron selection layer, and a metal electrode layer, which are stacked sequentially. The organic material blend layer is prepared by a two-layer sequential deposition method.

[0015] Preferably, the raw material of the conductive anode is any one of indium tin oxide, fluorine-doped tin dioxide, metal nanowires, graphene, nano-silver paste, carbon nanotubes, high-conductivity 3,4-ethylenedioxythiophene mixed polystyrene sulfonate, and materials with similar functions, which serves as the incident light window and has semi-transparent properties.

[0016] Preferably, the hole-selective layer is composed of a material with hole transport functionality, and is any one of organic p-type polymer materials, small molecule materials, metal oxide materials, and materials with similar functions. The polymer material is poly(4-butyltriphenylamine) (poly-TPD), 3,4-ethylenedioxythiophene mixed polystyrene sulfonate, etc. The small molecule material is 6,13-bis(triisopropylsilylethynyl)pentaphenyl, polyvinyldimethylphenazine, etc. The metal oxide material is molybdenum oxide, nickel oxide, etc.

[0017] Preferably, the organic material blend layer is composed of a blend of P-type and N-type materials, with the two types of materials distributed in a vertical gradient. The P-type layer is formed by layering or blending one or more organic materials with electron-donating properties, while the N-type layer is composed of organic materials with electron-withdrawing properties and is distributed in the middle or above the P-type layer. The thickness of the P-type material needs to reach the length that low-energy band tail photons of the N-type material can cross in the device. The total thickness of the organic material blend layer is 500–1500 nm. The P-type material is an organic conjugated polymer or conjugated small molecule material with electron-donating units, such as PTB7-Th, PM6, D18, etc. The N-type material is a non-fullerene electron acceptor material, such as IT-4F, Y6, COTIC-4F, etc.

[0018] Preferably, the electron selection layer is composed of a material with electron transport function, and is any one of low work function metal materials, water-soluble materials, and materials with similar functions. The water-soluble materials are derivatives of brominated-[9,9-dioctylfluorene-9,9-bis(N,N-dimethylaminopropyl)fluorene] (PFN-Br), polyethoxyethyleneimine (PEIE), naphthalenediimide (NDI), and perylenediimide (PDI), etc.

[0019] Preferably, the raw material composition of the metal electrode layer is any one of gold, silver, aluminum, copper, silver nanowires, conductive polymer films, alloy materials, and materials with similar functions, and its thickness is 50-150 nm.

[0020] The method for fabricating the narrow-band organic photodetector of the present invention is as follows:

[0021] Step 1: Clean and dry the glass substrate with the indium tin oxide conductive anode layer etched on its surface.

[0022] Step 2: Spin-coat the hole transport material onto the conductive electrode and anneal it to obtain the hole selection layer.

[0023] Step 3: Spin-coat the organic P-type material onto the hole selection layer, anneal it, and then spin-coat the N-type material onto the P-type material. After treatment, an organic material blend layer is obtained.

[0024] Step 4: Spin-coat the electron transport material onto the organic material blend layer to obtain the electron selection layer.

[0025] Step 5: Deposit a metal electrode onto the hole transport layer under a high vacuum environment.

[0026] Step 6: Package the obtained device to obtain an organic photodetector.

[0027] Compared with the prior art, the present invention has the following advantages and effects:

[0028] The narrowband organic photodetector of this invention has self-filtering properties, which can realize narrowband light detection function without the need for external filters or front layers, avoiding complex device structures, reducing the probability of signal crosstalk, and improving the signal-to-noise ratio of the detector.

[0029] The organic photoactive layer in this invention is prepared by sequential deposition of donor and acceptor materials. It utilizes the difference in solubility of the materials in different solvents to give it a unique vertical phase separation structure. The processed organic blend layer can simultaneously achieve effective separation of excitons and effective blocking of reverse electron-hole pairs in space. Compared with existing traditional thick heterojunction devices, it has higher quantum efficiency and lower noise current.

[0030] In the embodiments of the present invention, by using PTB7-Th as a thick donor material layer and IT-4F, Y6 and COTIC-4F as thin acceptor material layers, the fabricated device exhibits a dual-band narrowband optical response with a high-energy band tail absorption peak corresponding to the donor and a low-energy band tail absorption peak corresponding to the acceptor, and the absorption peak in the near-infrared region has a full width at half maximum (FWHM) of less than 100 nm.

[0031] The organic photodetector technology of this invention is simple and easy to implement, with a unique structure. By combining a simple and efficient spin coating process, it can achieve accurate and efficient detection capabilities, which has guiding significance for the large-scale industrial preparation of detectors in the field of narrow-band organic photodetectors and other related fields. Attached Figure Description

[0032] Figure 1 This is the external quantum efficiency spectrum curve of the organic photodetector in Embodiment 1 of the present invention.

[0033] Figure 2 This is the external quantum efficiency spectrum curve of the organic photodetector in Embodiment 2 of the present invention.

[0034] Figure 3 This is the dark current density-voltage characteristic curve of the organic photodetector in Embodiment 3 of the present invention.

[0035] Figure 4 This is the external quantum efficiency spectrum curve of the organic photodetector in Embodiment 3 of the present invention.

[0036] Figure 5 This is the specific detectivity spectrum curve of the organic photodetector in Embodiment 3 of the present invention. Detailed Implementation

[0037] The present invention will now be described in further detail with reference to specific embodiments.

[0038] Example 1:

[0039] A narrow-band organic photodetector, the structure of which comprises, from bottom to top, the following layers stacked sequentially: a glass substrate, a conductive anode, a hole selection layer, an organic material blend layer, an electron selection layer, and a metal electrode layer.

[0040] The conductive anode is indium tin oxide (ITO); the hole-selective layer is PEDOT:PSS (CH8000 model); the organic material blend layer is formed by sequentially depositing and blending P-type and N-type materials, where the P-type material is PTB7-Th and the N-type material is IT-4F; the electron-selective layer is PFN-Br; and the metal electrode layer is aluminum.

[0041] The above-mentioned method for fabricating organic photodetectors includes the following steps:

[0042] Step 1: Clean the glass substrate with the ITO layer on its surface by ultrasonic cleaning with surfactant, deionized water and isopropanol in sequence, each cleaning time is 15 minutes, and then put it in an oven at 70 degrees Celsius to dry for later use.

[0043] Step 2: Place the ITO substrate obtained in Step 1 under a vacuum of less than 100 Pa for oxygen plasma treatment for 3 minutes. Then spin coat the PEDOT:PSS dispersion solution onto the substrate at a speed of 2000 rpm for 40 seconds. Then place it on a hot stage at 150°C for annealing for 15 minutes to obtain a hole selection layer. Then transfer it to a glove box protected by nitrogen.

[0044] Step 3: Dissolve PTB7-Th in o-dichlorobenzene solvent, add 1% (v / v) of 1,8-diiodooctane as an additive, bringing the total material concentration to 13 mg / mL. Spin-coat the solution onto the hole-selective layer at 1500 rpm, heat-anneal at 100°C for 10 minutes, and then evacuate under vacuum for 1 hour to obtain the P-type layer. Dissolve IT-4F in chloroform solvent to a concentration of 40 mg / mL, spin-coat the solution onto the P-type layer at 2000 rpm, and heat-anneal at 80°C for 10 minutes to stabilize the combination, thus obtaining the organic material blend layer.

[0045] Step 4: Dissolve PFN-Br in methanol to a concentration of 0.5 mg / mL, and spin-coat it onto the organic material blend layer at a speed of 2000 rpm for 30 s to obtain the electron-selective layer.

[0046] Step 5: Place the substrate obtained in Step 4 into the photomask and transfer it to the evaporation chamber. Turn on the mechanical pump and molecular pump to evacuate the chamber, reducing the vacuum level to 4 × 10⁻⁶. -4 When the pressure is below Pa, the aluminum particles are heated to evaporate them and spiral upwards onto the electron transport layer, resulting in a thin metal film with a thickness of about 80 nm, which is the metal electrode layer.

[0047] Step 6: Apply an appropriate amount of encapsulating adhesive to the complete substrate obtained in Step 6, cover it with a transparent glass plate of suitable size, place it in an ultraviolet immersion apparatus, and cure it after 2 minutes of light exposure. Remove it to obtain the organic photodetector, and proceed to the next step of performance testing.

[0048] The organic photodetector prepared in Example 1 was subjected to relevant performance tests. Its external quantum efficiency spectrum obtained under no bias voltage is shown below. Figure 1 As shown, it exhibits obvious dual-band narrowband characteristics, with a full width at half maximum (FWHM) of approximately 50 nm in the narrowband response at 700-900 nm in the near-infrared region.

[0049] Example 2:

[0050] A narrow-band organic photodetector, the structure of which comprises, from bottom to top, the following layers stacked sequentially: a glass substrate, a conductive anode, a hole selection layer, an organic material blend layer, an electron selection layer, and a metal electrode layer.

[0051] The conductive anode is indium tin oxide (ITO); the hole-selective layer is PEDOT:PSS (AI4083 type); the organic material blend layer is formed by sequentially depositing and blending P-type and N-type materials, where the P-type material is PTB7-Th and the N-type material is Y6; the electron-selective layer is PFN-Br; and the metal electrode layer is silver.

[0052] The above-mentioned method for fabricating organic photodetectors includes the following steps:

[0053] Step 1: The glass substrate with the ITO layer on its surface is ultrasonically cleaned repeatedly with surfactant, deionized water and isopropanol, each cleaning time is 15 minutes. Then it is dried with a nitrogen gun and placed in a petri dish for later use.

[0054] Step 2: Place the ITO substrate obtained in Step 1 in an oxygen plasma chamber with a vacuum of less than 100 Pa for 3 minutes. Then spin-coat the substrate with a deionized water dispersion of PEDOT:PSS at 2000 rpm for 40 seconds. Then place it on a hot stage at 150°C for annealing for 15 minutes to obtain a hole-selective layer. Then transfer it to a glove box under nitrogen protection.

[0055] Step 3: Dissolve PTB7-Th in chlorobenzene solvent to a concentration of 15 mg / mL, spin-coat it onto the hole-selective layer at 1500 rpm, and heat-anneal at 120°C for 10 minutes to obtain the P-type layer. Dissolve Y6 in chloroform solvent to a concentration of 30 mg / mL, spin-coat it onto the P-type layer at 2000 rpm, and allow it to stand for a period of time to allow the two to combine and stabilize, thus obtaining the organic material blend layer.

[0056] Step 4: Dissolve PFN-Br in methanol to a concentration of 0.5 mg / mL, and spin-coat it onto the organic material blend layer at a speed of 2000 rpm for 30 s to obtain the electron-selective layer.

[0057] Step 5: Place the substrate obtained in Step 4 into the photomask and transfer it to the evaporation chamber. Turn on the mechanical pump and molecular pump to evacuate the chamber, reducing the vacuum level to 4 × 10⁻⁶. -4 When the pressure is below Pa, the silver particles are heated to evaporate them and then spiral upwards onto the electron transport layer, resulting in a thin metal film with a thickness of about 100 nm, which is the metal electrode layer.

[0058] Step 6: Apply an appropriate amount of encapsulating adhesive to the complete substrate obtained in Step 6, cover it with a transparent glass plate of suitable size, place it in an ultraviolet immersion apparatus, and cure it after 2 minutes of light exposure. Remove it to obtain the organic photodetector, and proceed to the next step of performance testing.

[0059] The organic photodetector prepared in Example 2 was subjected to relevant performance tests. Its external quantum efficiency spectrum obtained under no bias voltage is shown below. Figure 2 As shown, it exhibits obvious dual-band narrowband characteristics, with a full width at half maximum (FWHM) of approximately 50 nm in the narrowband response at 850-1000 nm in the near-infrared region.

[0060] Example 3:

[0061] A narrow-band organic photodetector, the structure of which comprises, from bottom to top, the following layers stacked sequentially: a glass substrate, a conductive anode, a hole selection layer, an organic material blend layer, an electron selection layer, and a metal electrode layer.

[0062] The conductive anode is indium tin oxide (ITO); the hole-selective layer is PEDOT:PSS (CH8000 model); the organic material blend layer is formed by sequentially depositing and blending P-type and N-type materials, where the P-type material is PTB7-Th and the N-type material is COTIC-4F; the electron-selective layer is PFN-Br; and the metal electrode layer is aluminum.

[0063] The above-mentioned method for fabricating organic photodetectors includes the following steps:

[0064] Step 1: The glass substrate with the ITO layer on its surface is ultrasonically cleaned repeatedly with surfactant, deionized water and isopropanol, each cleaning time is 15 minutes. Then it is dried with a nitrogen gun and placed in a petri dish for later use.

[0065] Step 2: Place the ITO substrate obtained in Step 1 in an oxygen plasma chamber with a vacuum of less than 100 Pa for 3 minutes. Then spin-coat the substrate with a deionized water dispersion of PEDOT:PSS at 2000 rpm for 40 seconds. Then place it on a hot stage at 150°C for annealing for 15 minutes to obtain a hole-selective layer. Then transfer it to a glove box under nitrogen protection.

[0066] Step 3: Dissolve PTB7-Th in chlorobenzene solvent, add 2% (v / v) of chloronaphthalene additive, bringing the total material concentration to 16 mg / mL. Spin-coat the mixture onto the hole-selective layer at 1300 rpm, and heat-anneal at 110°C for 10 minutes to obtain the P-type layer. Dissolve COTIC-4F in chloroform solvent to a concentration of 30 mg / mL, spin-coat the mixture onto the P-type layer at 2000 rpm, and heat-anneal at 110°C for 10 minutes to stabilize the combination, thus obtaining the organic material blend layer.

[0067] Step 4: Dissolve PFN-Br in methanol to a concentration of 0.5 mg / mL, and spin-coat it onto the organic material blend layer at a speed of 2000 rpm for 30 s to obtain the electron-selective layer.

[0068] Step 5: Place the substrate obtained in Step 4 into the photomask and transfer it to the evaporation chamber. Turn on the mechanical pump and molecular pump to evacuate the chamber, reducing the vacuum level to 4 × 10⁻⁶. -4 When the pressure is below Pa, the aluminum particles are heated to evaporate them and spiral upwards onto the electron transport layer, resulting in a thin metal film with a thickness of about 80 nm, which is the metal electrode layer.

[0069] Step 6: Apply an appropriate amount of encapsulating adhesive to the complete substrate obtained in Step 6, cover it with a transparent glass plate of suitable size, place it in an ultraviolet immersion apparatus, and cure it after 2 minutes of light exposure. Remove it to obtain the organic photodetector, and proceed to the next step of performance testing.

[0070] The organic photodetector prepared in Example 3 was subjected to relevant performance tests, and its dark current density-voltage characteristic curve is shown below. Figure 3 As shown, it has a low voltage of 2.9 × 10⁻⁶ at a bias voltage of -0.1V. -9 A / cm 2 The dark current density value, and the external quantum efficiency spectrum obtained by the test are as follows: Figure 4 As shown, it exhibits obvious dual-band narrowband characteristics, with a full width at half maximum (FWHM) of approximately 70 nm in the narrowband response in the near-infrared region (1000-1200 nm). Its specific detectivity curve is shown in Figure 1. Figure 5 As shown, it has a high strength of 2.8 × 10⁻⁶ at the 1070 nm peak. 12 Jones.

[0071] As described above, the present invention can be implemented well.

[0072] The organic material blend layer of this invention is prepared by a two-layer sequential deposition method, and is composed of a blend of P-type and N-type materials. The two types of materials are distributed in a vertical gradient in space, which enables the device to simultaneously achieve effective separation of excitons and effective blocking of reverse electron-hole pairs. Compared with existing traditional thick heterojunction devices, it has higher quantum efficiency and lower noise current.

[0073] This invention achieves narrowband light detection functionality through a novel device structure and simple processing technology by controlling the organic material blend layer, without the need for external filters or pre-layers. It has particularly accurate and efficient detection capabilities in the near-infrared region and has significant application prospects.

[0074] The embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A narrow-band organic photodetector, characterized in that: The structure of the narrow-band organic photodetector includes, from bottom to top, the following layers stacked in sequence: a glass substrate, a conductive anode layer, a hole selection layer, an organic material blend layer, an electron selection layer, and a metal electrode layer. The organic material blend layer was prepared by a two-layer sequential deposition method, first depositing a P-type material layer and then depositing an N-type material layer. The P-type material layer and the N-type material layer are distributed in a vertical gradient; The P-type material layer is formed by layering or blending one or more organic materials with electron-donating properties; The N-type material layer is composed of organic materials with electron-withdrawing properties and is distributed in the middle or above the P-type material layer; The thickness of the P-type material layer needs to reach the length that the low-energy band tail photons of the N-type material layer can cross in the device. The P-type material layer is an organic conjugated polymer with electron-donating units, selected from PTB7-Th, PM6, and D18; The N-type material layer is a non-fullerene electron acceptor material selected from IT-4F, Y6, and COTIC-4F; the total thickness of the organic material blend layer is 500–1500 nm.

2. The narrow-band organic photodetector according to claim 1, characterized in that: The conductive anode layer is made from any one of the following: indium tin oxide, fluorine-doped tin dioxide, metal nanowires, graphene, silver nanopaste, carbon nanotubes, or high-conductivity 3,4-ethylenedioxythiophene mixed polystyrene sulfonate, and serves as the incident light window.

3. The narrow-band organic photodetector according to claim 1, characterized in that: The hole selective layer is composed of a material with hole transport function, and is any one of poly(4-butyltriphenylamine), 3,4-ethylenedioxythiophene mixed polystyrene sulfonate, 6,13-bis(triisopropylsilylethynyl)pentabenzene, polyvinyl dimethylphenazine, molybdenum oxide and nickel oxide.

4. The narrow-band organic photodetector according to claim 1, characterized in that: The electron-selective layer is a derivative of brominated-[9,9-dioctylfluorene-9,9-bis(N,N-dimethylaminopropyl)fluorene], polyethoxyethyleneimine, and naphthalimide or perylene diimide.

5. The narrow-band organic photodetector according to claim 1, characterized in that: The raw material composition of the metal electrode layer is gold, silver, aluminum, copper, silver nanowires and / or conductive polymer films.

6. A method for fabricating the narrow-band organic photodetector according to any one of claims 1-5, characterized in that... Includes the following steps: S1: Clean and dry the glass substrate with the conductive anode layer etched on its surface; S2: Hole transport material is spin-coated onto a conductive electrode and annealed to obtain a hole selection layer; S3: Spin-coat the organic P-type material onto the hole selection layer, anneal it, and then spin-coat the N-type material onto the P-type material. After treatment, an organic material blend layer is obtained. S4: Electron transport material is spin-coated onto an organic material blend layer to obtain an electron selection layer; S5: Metal electrodes are deposited on the hole transport layer under high vacuum conditions; S6: Package the obtained device to obtain a narrow-band organic photodetector.

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