An organic photodetector array that can amplify and detect weak light signals

Abstract

The present invention provides an organic photodetector array that can amplify and detect weak light signals. The array is composed of a substrate, a first electrode, an interface layer, a light absorbing active layer, an interface layer, and a second electrode stacked in sequence. More than two basic device units are prepared on the substrate, and a series detection array is formed by connecting the device units in series in sequence with wires. Under working conditions, all device units in the array can convert the detected weak light signals into voltage signals and achieve the multiplication of the photovoltage amplitude, and the multiplication number is roughly the same as the number of basic device units in series. The organic photodetector array obtained by this method can directly detect and convert weak light signals into electrical signals for amplification and output without the need for additional electrical signal amplifiers or systems, thereby greatly reducing the geometric size occupied by the detector array, simplifying the product design, and having strong versatility and compatibility in the field of wearable electronic devices.

Description

Technical Field

[0001] The present invention relates to the field of organic photodetectors and wearable devices, in particular to the field of photodetection and wearable medical technology, and specifically to a design scheme and technology for preparing an organic photodetector array capable of detecting and amplifying weak signals. Background Art

[0002] The next generation of wearable electronic devices often need to be flexible, bendable, and easy to miniaturize so that they can better adhere to the human body. Organic semiconductor optoelectronic devices with organic materials as active substances can meet the above requirements and can be prepared on a large scale at a low cost. Therefore, they are expected to have huge development space in the field of new wearable electronic devices. At present, common wearable electronic products on the market, such as smart bracelets and smart watches, generally integrate electronic components on the bracelet or dial. In addition to basic functions such as time display and weather forecast, they can also monitor the changes in human pulse and blood oxygen value in real time, which has initially achieved the purpose of wearable medical monitoring.

[0003] However, the wearable biomedical electronic devices currently on the market are still a long way from achieving true wearable functions, and the main gap lies in their lack of flexibility and bendability. For example, for existing smart watches, to achieve real-time monitoring and detection functions of biomedical signals such as pulse and blood oxygen saturation, it is necessary to integrate two modules: semiconductor light-emitting diodes (LEDs) as signal source light and semiconductor photodetectors (PDs) as signal receivers. The LEDs and PDs currently used in the market are all made based on inorganic semiconductor materials. Due to the rigidity limitations of inorganic materials and devices in mechanical properties, they are often unable to withstand the necessary mechanical bending and folding, and thus cannot meet the requirements of the next generation of wearable electronic devices for flexibility. In sharp contrast, organic matter has the characteristics of flexibility, bendability and foldability. Organic light-emitting diodes OLED and organic photodetectors OPD based on organic polymers, small molecules and other materials are easy to prepare flexible devices of various shapes to adapt to various applications. In addition, due to the rich and diverse molecular structures of organic materials, their electronic energy level structures can be adjusted over a wide range, thereby producing spectral responses to incident light of different wavelengths.

[0004] The use of organic optoelectronic devices in wearable electronic devices and medical monitoring applications is often limited by the weak signals to be detected and requires the use of complex electronic signal amplifiers or modules. Taking the photoplethysmogram (PPG) signal, which can be used to monitor the changes in blood volume in the microvascular bed of human tissue, as an example, to obtain a reliable photoplethysmogram signal, it is generally obtained through professional medical testing instruments and equipment, such as a pulse oximeter. The working principle of the pulse oximeter is to illuminate the skin with a specific light source and then detect the changes in light absorption. Traditional oximeters obtain PPG signals by monitoring the blood perfusion of the dermis and subcutaneous tissue. Generally speaking, the photoplethysmogram signal PPG is very weak. After the photoplethysmogram signal is detected by a photodetector, it is often necessary to use a transimpedance amplifier to amplify it and output it in the form of voltage for subsequent signal processing. This requires an additional signal amplification module, which undoubtedly reduces the overall flexibility of the system and limits the functions of wearable electronic devices. The present invention describes a preparation method, which can obtain an organic photodetector array capable of amplifying and detecting weak light signals without using an electronic signal amplification module, and apply it to detect photoplethysmographic signals of blood volume changes in the microvascular bed of human tissue. Summary of the invention

[0005] The present invention provides an organic photodetector array that is compatible with wearable electronic detection and diagnostic equipment and can amplify and detect weak light signals. This photodetector array effectively amplifies and detects weak signals to be detected (such as photoplethysmographic signals in human tissue) without the need for any additional electronic amplification components.

[0006] The content of the present invention is achieved through the following technical solutions:

[0007] An organic photodetector array capable of amplifying and detecting weak light signals, characterized in that the unit device structure of the array sequentially comprises a substrate, a first electrode, an interface layer, an organic light absorbing active layer, an interface layer, and a second electrode;

[0008] A plurality of independent photodetector device units are prepared on a substrate, and the positive and negative electrodes of the independent photodetector units are connected end to end by wire connection to form a photodetector array in series;

[0009] All independent device units can convert the detected weak light signals into voltage signals and realize the multiplication of the photovoltage amplitude. The multiplication number is roughly the same as the number of basic device units connected in series, thereby achieving the effect of amplifying the output photovoltage signal.

[0010] Furthermore, an upright or inverted device structure is used; in the upright structure, the first electrode is the anode and the second electrode is the cathode; in the inverted structure, the second electrode is the anode and the first electrode is the cathode.

[0011] Furthermore, the organic light absorbing active layer with photoelectric response function is obtained by one of the processing and preparation methods such as solution spin coating, scraping, screen printing, inkjet printing, spraying or vacuum thermal evaporation film forming; the light absorbing active layer is a semiconductor body heterojunction formed by mixing an organic electron donor material and an organic electron acceptor material, or a semiconductor composed of an organic electron donor layer / organic electron acceptor layer.

[0012] Furthermore, the organic electron donor material in the organic light absorbing active layer is an organic conjugated small molecule, oligomer or polymer.

[0013] Furthermore, the organic electron acceptor type material in the organic light absorbing active layer is fullerene and its derivatives, organic conjugated small molecules, oligomers, and polymers.

[0014] Furthermore, the interface layer and the interfacial layer are made of one or more combinations of organic materials and metal oxide materials.

[0015] Furthermore, the electrodes and electrodes include any one or more of inorganic electrode materials, organic electrode materials, and metal electrode materials, or materials with similar functions.

[0016] Furthermore, the substrate is any one or more composites of glass, paper, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide (PI), polyetherimide (PEI), etc., or materials with similar functions. Preferably, the substrate is glass.

[0017] Furthermore, the inorganic electrode material includes indium tin oxide ITO, metal nanowires, nano silver paste, and aluminum-doped zinc oxide AZO.

[0018] Furthermore, the organic electrode material is high-conductivity 3,4-ethylenedioxythiophene mixed polystyrene sulfonate (PEDOT:PSS), carbon nanotubes (CNT) or graphene; the metal electrode material includes one or more of lithium, magnesium, calcium, strontium, barium, aluminum, copper, gold, silver and indium.

[0019] Further, the first electrode and the second electrode materials are any one or more of inorganic electrode materials (such as indium tin oxide (ITO), metal nanowires, nanosilver paste, aluminum-doped zinc oxide (AZO), etc.), organic electrode materials (such as high-conductivity 3,4-ethylenedioxythiophene mixed polystyrene sulfonate (PEDOT:PSS), diimine dioxyimino (PDINO), carbon nanotubes (CNT), graphene, etc.), and metal electrode materials (such as lithium, magnesium, calcium, strontium, barium, aluminum, copper, gold, silver, indium, etc.), or materials with similar functions. Preferably, the electrode 2 is indium tin oxide, and the electrode 6 material is silver.

[0020] Further, the donor material is a conjugated polymer material or other electron donor material containing a conjugated structure. Preferably, the organic donor material is poly[2,6-(4,8-bis(5-(2-ethylhexyl))thiophene-2-yl)-benzo[1,2-b:4,5-b']dithiophene-alt-5,5-(1',3'-di-2-thiophene)-5',7'-bis(2-ethylhexyl)-benzo[1',2'-c:4',5'-c']dithiophene-4,8-dione](PBDB-T), poly[4,8-bis(5(2-ethylhexyl)thiophene-2)benzo[1,2-b;4,5-b']polythiophene 2,6-bis(4-(2-ethylhexyl)-3-fluoro[3,4-b]thiophene)2-carboxylic acid-2-6-diyl)](PTB7-Th).

[0021]

[0022] Further, the organic acceptor material is an electron acceptor material such as fullerene and its derivatives, organic conjugated small molecules, oligomers, polymers, etc. Preferably, the organic acceptor material is a non-fullerene electron acceptor material (3,9-(2-methylbenzene-(3-(1,1-dicyanamideethylene)-5 / 6-methylamphetamine)-5,5,11,11-tetrayl(4-hexaphenyl)-dithiophene[2,3-d:2',3'-d'-s-indacene[1,2-b:5,6-b']disulfide) (IT-M), 2-((E)-2-((5-(6-(5-((Z)-1-(di =The results are as follows: (1,2-difluoro-3-oxo-2,3-2H-2-ylidene)-2,4-dihydrogen-1-ylidene)-5,6-difluoro-3-oxo-1,3-2H-2-ylidene)-2,4-dihydrogen-1 ...

[0023] Compared with the prior art, the present invention has the following characteristics and advantages:

[0024] (1) The photodetector array of the present invention is integrated in series on a single substrate via wires, and can achieve multiple amplification and detection of weak light signals without the need for additional electronic signal amplifiers or modules.

[0025] (2) The photodetector array of the present invention has a photoactive layer made of organic matter and can be prepared on various flexible substrates and base materials. It has the technical characteristics of being bendable and foldable, and is highly compatible with wearable devices and medical detection and diagnostic instruments that have high requirements for bendability. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a cross-sectional view of an organic photodetector array capable of amplifying and detecting weak light signals described in the present invention, wherein a substrate 1 , an electrode 2 , an interface layer 3 , a light absorbing active layer 4 , an interface layer 5 and an electrode 6 are provided.

[0027] Figure 2 This is a top view of an organic photodetector array capable of amplifying and detecting weak light signals described in the present invention, wherein a substrate 1 , an electrode 2 and an electrode 6 are provided.

[0028] Figure 3 Schematic diagram of an organic photodetector array that can amplify and detect weak light signals described in the present invention.

[0029] Figure 4a The present invention describes an organic photodetector array that can amplify and detect weak light signals, and uses a specific example of detecting photoplethysmographic signals in human tissue. By using one device in series, the effect is achieved that the amplitude of the photoplethysmographic signal increases with the increase in the number of devices in series.

[0030] Figure 4b The present invention describes an organic photodetector array that can amplify and detect weak light signals, and uses a specific example of detecting photoplethysmographic signals in human tissue. Three devices are connected in series, and the effect is obtained that the amplitude of the photoplethysmographic signal increases with the increase in the number of devices connected in series.

[0031] Figure 4c The present invention describes an organic photodetector array that can amplify and detect weak light signals, and uses a specific example of detecting photoplethysmographic signals in human tissue. Six devices are connected in series, and the effect is obtained that the amplitude of the photoplethysmographic signal increases with the increase in the number of devices connected in series. DETAILED DESCRIPTION

[0032] The following examples will illustrate the specific process proposed by the present invention, but the present invention is not limited to the examples listed.

[0033] Example 1

[0034] like Figure 1 As shown, a photodetector signal amplification array capable of amplifying weak signals has a device structure comprising a substrate 1, an electrode 2, an interface layer 3, a light absorbing active layer 4, an interface layer 5 and an electrode 6 in sequence.

[0035] The device structure is an inverted device structure; the substrate 1 is glass; the electrode 2 is a cathode-indium tin oxide (ITO); the interface layer 3 is a cathode interface layer-zinc oxide (ZnO); the light absorption layer 4 is a blended film of PBDB-T electron donor and IT-M electron acceptor; the interface layer 5 is an anode interface layer-molybdenum trioxide (MoO 3 ); the electrode 5 is anode-silver.

[0036] Several ITO conductive glass substrates of the same batch number, with specifications of 15 mm × 15 mm, the thickness of ITO is about 130 nanometers, and its square resistance is about 20 ohms / square. Place the ITO glass on a stand, put the stand into a beaker of suitable size, pour isopropyl alcohol into the beaker, immerse the ITO glass, and ultrasonically clean it for 15-20 minutes; then pour out the isopropyl alcohol, use deionized water to ultrasonically clean it three times according to the above process, each time for 15-20 minutes, and finally use isopropyl alcohol to clean it again according to the above process, also for 15-20 minutes. After the end, pour out the isopropyl alcohol and place the beaker containing the ITO glass in an oven for drying.

[0037] The inverted photodetector of the present invention uses zinc oxide as the cathode interface layer. The preparation process of the zinc oxide precursor solution is to add 1g zinc acetate, 10ml 2-methoxyethanol, and 280μl ethanolamine, and stir and heat at 60°C overnight. Then, ZnO is spin-coated on the glass substrate 1 / cathode 2 by spin coating, with a thickness of 30nm.

[0038] Then, the glass substrate 1 / cathode 2 / cathode interface layer 3 prepared by the above method was transferred into a special glove box (manufactured by VAC, USA) that was anhydrous and oxygen-free and filled with high-purity nitrogen. In the inert atmosphere of this glove box, the organic donor material PBDB-T and the organic acceptor material IT-M were placed in a clean sample bottle in a ratio of 1:1 and dissolved with an organic solvent chlorobenzene. After being completely dissolved, they were spin-coated on ZnO using a coating machine with a thickness of 100 nanometers.

[0039] Then, the device was transferred into the vacuum deposition chamber, and the mechanical pump and molecular pump were turned on. When the pressure in the vacuum deposition chamber was reduced to 2×10 -6 After that, 10nm thick MoO was evaporated. 3 As the anode interface layer 5 and 100 nm thick silver as the anode 6.

[0040] Example 2

[0041] Repeat Example 1, using a blended film of PTB7-Th electron donor and COTIC-4F electron acceptor as the active layer, so that the device can detect infrared signals. Other conditions remain unchanged. Put the organic donor material PTB7-Th and the organic electron acceptor material COTIC-4F in a clean sample bottle at a ratio of 1:1.5, and dissolve them with organic solvent chloroform. After thorough dissolution, use a coating machine to spin coat it on the cathode interface layer, with a thickness of 100nm.

[0042] Example 3

[0043] like Figure 1 As shown, a photodetector signal amplification array capable of amplifying weak signals has a device structure comprising a substrate 1, an electrode 2, an interface layer 3, a light absorbing active layer 4, an interface layer 5 and an electrode 6 in sequence.

[0044] The device structure is an upright device structure; the substrate 1 is glass; the electrode 2 is an anode-indium tin oxide (ITO); the interface layer 3 is an anode interface layer-PEDOT:PSS; the light absorption layer 4 is a blended film of PBDB-T electron donor and IT-M electron acceptor; the interface layer 5 is a cathode interface layer-PDINO; and the electrode 5 is an anode-silver.

[0045] Several ITO conductive glass substrates of the same batch number, with specifications of 15 mm × 15 mm, the thickness of ITO is about 130 nanometers, and its square resistance is about 20 ohms / square. Place the ITO glass on a stand, put the stand into a beaker of suitable size, pour isopropyl alcohol into the beaker, immerse the ITO glass, and ultrasonically clean it for 15-20 minutes; then pour out the isopropyl alcohol, use deionized water to ultrasonically clean it three times according to the above process, each time for 15-20 minutes, and finally use isopropyl alcohol to clean it again according to the above process, also for 15-20 minutes. After the end, pour out the isopropyl alcohol and place the beaker containing the ITO glass in an oven for drying.

[0046] The upright photodetector in the present invention uses PEDOT:PSS as the anode interface, and PEDOT:PSS is spin-coated onto the glass substrate 1 / anode 2 by spin coating, with a thickness of 30 nm.

[0047] Then, the glass substrate 1 / anode 2 / anode interface layer 3 prepared by the above method was transferred into a dedicated glove box (manufactured by VAC, USA) that was free of water and oxygen and filled with high-purity nitrogen. In the inert atmosphere of this glove box, the organic donor material PBDB-T and the organic acceptor material IT-M were placed in a clean sample bottle in a ratio of 1:1 and dissolved with an organic solvent chlorobenzene. After being completely dissolved, they were spin-coated on PEDOT:PSS using a coating machine with a thickness of 100nm.

[0048] PDINO was dissolved in methanol solution with a concentration of 1-2 mg / ml and then spin-coated on the active layer as a cathode interface layer with a thickness of 30 nm.

[0049] Then, the device was transferred into the vacuum deposition chamber, and the mechanical pump and molecular pump were turned on. When the pressure in the vacuum deposition chamber was reduced to 2×10 -6 After that, 10nm thick MoO was evaporated. 3 As the anode interface layer 5 and 100 nm thick silver as the anode 6.

[0050] Example 4

[0051] Repeat Example 3, using a blended film of PTB7-Th electron donor and COTIC-4F electron acceptor as the active layer, so that the device can detect infrared signals. Other conditions remain unchanged. Put the organic donor material PTB7-Th and the organic electron acceptor material COTIC-4F in a clean sample bottle at a ratio of 1:1.5, and dissolve them with organic solvent chloroform. After thorough dissolution, use a coating machine to spin coat it on the cathode interface layer, with a thickness of 100nm.

[0052] Figure 1 A cross-sectional view of the structure of an organic photodetector device capable of amplifying and detecting weak light signals described in the present invention is given, wherein from bottom to top are a substrate 1, an electrode 2, an interface layer 3, a light absorbing active layer 4, an interface layer 5 and an electrode 6.

[0053] Figure 2 A top view of the organic photodetector device described in the present invention that can amplify and detect weak light signals is given. Six independent organic photodetector devices can be observed on the top view device plane, wherein the substrate 1, electrode 2 and electrode 6 can be observed by human eyes.

[0054] Figure 3 The schematic diagram of the organic photodetector array described in the present invention that can amplify and detect weak light signals is given. Figure 2 The six independent devices observable in the figure are connected in series and integrated on a single substrate, so weak light signals can be amplified and detected exponentially without the need for additional electronic signal amplifiers or modules.

[0055] Figure 4a to Figure 4c The PPG photovoltage signal is given after the weak PPG light signal is amplified by the photodetector signal amplification array of the present invention. It can be seen that when only one device is working, the amplitude of the PPG signal is only 7mV; when three devices are connected in series, the amplitude of the PPG signal reaches 17mV, and when six devices are connected in series, the amplitude of the PPG signal reaches 26mV.

[0056] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. An organic photodetector array capable of amplifying and detecting weak light signals, characterized in that: The unit device structure of the array comprises, in sequence, a substrate (1), a first electrode (2), an interface layer (3), an organic light absorption active layer (4), an interface layer (5), and a second electrode (6); A plurality of independent photodetector device units are prepared on a substrate, and the positive and negative electrodes of the independent photodetector units are connected end to end by wire connection to form a photodetector array in series; All independent device units can convert the detected optical signals into voltage signals and realize the multiplication of the photovoltage amplitude. The multiplication number is the same as the number of basic device units connected in series, thereby achieving the effect of amplifying the output photovoltage signal. The organic light absorbing active layer (4) with photoelectric response function is obtained by one of the following film forming processing methods: solution spin coating, scraping, screen printing, inkjet printing, spray coating or vacuum thermal evaporation; the light absorbing active layer (4) is composed of a semiconductor composed of an organic electron donor layer / organic electron acceptor layer; The organic electron donor material in the organic light absorbing active layer (4) is an organic conjugated small molecule, oligomer or polymer; The organic electron acceptor type material in the organic light absorbing active layer (4) is fullerene and its derivatives, organic conjugated small molecules, oligomers, and polymers; The electrode (2) and the electrode (6) include any one or more of an inorganic electrode material and an organic electrode material; The inorganic electrode material includes indium tin oxide ITO, nano silver paste, and aluminum-doped zinc oxide AZO; The organic electrode material is high-conductivity 3,4-ethylenedioxythiophene mixed polystyrene sulfonate PEDOT:PSS, carbon nanotube CNT or graphene.

2. The organic photodetector array capable of amplifying and detecting weak light signals according to claim 1, characterized in that: An upright or inverted device structure is used; in the upright structure, the first electrode (2) is an anode and the second electrode (6) is a cathode; in the inverted structure, the second electrode (6) is an anode and the first electrode (2) is a cathode.

3. The organic photodetector array capable of amplifying and detecting weak light signals according to claim 1, characterized in that: The interface layer (3) and the interface layer (5) are made of one or more combinations of organic materials and metal oxide materials.

4. The organic photodetector array capable of amplifying and detecting weak light signals according to claim 1, characterized in that The substrate (1) is made of any one of glass, paper, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide (PI), and polyetherimide (PEI).

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