Organic Vertical Diodes Integrating Transient Optical Detection and Optical Synaptic Functions and Their Applications

Abstract

The present invention relates to a multifunctional organic vertical diode integrating transient optical detection and optical synaptic functions and its applications. The structure sequentially includes a substrate, an anode layer, a hole transport layer, an active layer, an electron transport layer, and a metal cathode. On the substrate, the anode layer is coated, and then the hole transport layer, the active layer, the electron transport layer, and the metal cathode are sequentially evaporated or spin-coated to obtain the multifunctional organic vertical diode. This device is used as an optical synapse under forward bias, exhibits a long memory time, and realizes the association learning of "quenching one's thirst by thinking of plums" and high image recognition accuracy. The present invention realizes for the first time a multifunctional organic vertical diode integrating transient optical detection and optical synaptic functions, and is also the first realization of a two-terminal vertical optical synapse, providing effective space and weight savings for space-constrained applications (including wearable devices, smartphones, and other portable consumer electronic products), and reducing energy consumption.

Description

Technical Field

[0001] The present invention relates to the field of optoelectronic sensing, and particularly to an organic vertical diode integrating transient light detection and optosynaptic functions, a preparation method thereof, and applications in contactless heart rate detection and image recognition. Background Art

[0002] Organic materials are an important part of solution-processed semiconductors and have attracted intense research interest due to their wide availability, tunable optoelectronic properties by molecular design, biocompatibility, light weight, and flexibility. Over the past few decades, significant progress has been made in organic materials for solar cells, photodetectors, light-emitting diodes, field-effect transistors, and memristors. Recently, there has been growing interest in multifunctional organic devices. The combination of photovoltaic and light-emitting functions in organic photodiodes is of great significance in flexible and wearable electronics. Transient light detection and optosynaptic functions modulated by the gate voltage of organic transistors have broad application prospects in the field of organic multifunctional devices. Organic light-emitting transistors integrating the amplification and switching characteristics of electroluminescence and field-effect transistors are of great significance for the development of miniaturized and integrated optoelectronic devices. Multifunctional devices replace multiple devices with a single device, which not only provides effective space and weight savings for space-constrained applications (including wearable devices, smartphones, and other portable consumer electronics), but also reduces energy consumption. However, there are few photodiodes that combine transient light detection and optosynaptic functions.

[0003] With the development of big data and artificial intelligence, due to the separation of the storage and processing units in the traditional von Neumann architecture, it can no longer meet people's demands for low energy consumption and efficient parallel processing. At the same time, neuromorphic computing that mimics the working principle of the human brain has also attracted great interest. Simulating biological synapses is a necessary step in constructing neuromorphic computing in hardware. 80% of the external information of the human body is obtained through visual perception. The human visual system integrates the abilities of perception, processing, and memory. The information obtained by the human eye is preprocessed by the retina and transmitted to the visual cortex of the brain through the optic nerve, where some key features are extracted. The simulation of optoelectronic synapses is of great significance for bionic visual systems and neuro-optoelectronic computing. Photonic synapses modulated by optical signals instead of electrical signals not only are expected to overcome the high energy consumption, high crosstalk, and low bandwidth of electrical synapses, but also have the advantages of high speed, wavelength division multiplexing ability, non-contact writing and erasing operations, etc. However, despite the great progress made in optoelectronic synapses, few vertical diode-type organic optoelectronic synapses have been reported so far. Exploring new structures to fabricate organic optoelectronic synapses is crucial for constructing neuromorphic computing in hardware. At the same time, organic near-infrared (NIR) photodetectors are considered to be strong candidates for optical communication, biological imaging, machine vision, medical monitoring, and quality monitoring due to their unique advantages. Integrating transient light detection and optosynaptic functions in the same device is of great significance for multifunctional and miniaturized photonic integrated systems. Summary of the Invention

[0004] Aiming at the problems existing in the above-mentioned prior art, the primary object of the present invention is to provide a preparation method of a multifunctional organic vertical diode and its applications in non-contact heart rate detection and image recognition. When the device is used as a photodetector under a negative bias voltage, it has the characteristics of high detectivity, large linear dynamic range, and low noise current. When used for PPG (photoplethysmography) testing, it can distinguish the heart rates in resting and exercising states. When the device is used as an optosynapse under a positive bias voltage, it has the characteristics of weak light response, long state retention time, and low energy consumption. When applied to neural network image recognition, an identification accuracy of more than 80% is achieved.

[0005] The object of the present invention is achieved by the following technical solutions:

[0006] A multifunctional organic vertical diode integrating transient light detection and optosynaptic functions, characterized in that the structure sequentially includes a substrate, an anode layer, a hole transport layer, an active layer, an electron transport layer, and a metal cathode;

[0007] On the substrate, an anode layer is coated, and then the hole transport layer, the active layer, the electron transport layer, and the metal cathode are sequentially evaporated or spin-coated to obtain the multifunctional organic vertical diode.

[0008] The hole transport layer is a hole transport layer material such as poly-TPD or PEDOT:PSS.

[0009] The electron donor material of the active layer is an organic p-type material such as PM7, PTB7-Th, or PM6; the electron acceptor material of the active layer is an organic n-type material such as PCBM, IEICO-4F, ITIC, or Y6.

[0010] The electron transport layer is other electron transport layer materials such as water-alcohol soluble materials PFN, PFN-Br, and PEIE.

[0011] The metal cathode is Al, Ag, or Au, and the anode is ITO or a conductive organic polymer.

[0012] The electron transport layer is other electron transport layer materials such as PDINO, PDINN, C70, and C60.

[0013] The active layer is a blend film of an organic p-type material P3HT and an organic n-type material PCBM (the donor-acceptor ratio is 1:1), or a blend film of an organic p-type material PTB7-Th and an organic n-type material IEICO-4F (the donor-acceptor ratio is 1:1.2), and other possible organic blend heterojunction structures.

[0014] A method for preparing a multifunctional organic vertical diode integrating transient light detection and photonic synaptic functions is as follows:

[0015] ⑴ The substrate coated with the anode is sequentially cleaned with soapy water, deionized water, acetone, ethanol, and ultrasonic cleaning for 15 - 30 min, then dried with a nitrogen gun, and subsequently treated with ultraviolet ozone for 30 min as the anode;

[0016] ⑵ Spin-coat the hole transport layer on the anode;

[0017] ⑶ Spin-coat the active layer composed of a bulk heterojunction mixed solution of an organic p-type material and an organic n-type material on the hole transport layer at a suitable rotation speed;

[0018] ⑷ Spin-coat the electron transport layer on the active layer at a suitable rotation speed; evaporate 100 nanometers of the cathode metal through the vacuum evaporation method of the vapor deposition system. The overlapping part of the cathode metal and the anode ITO is the effective area of the device, which is 0.04 square centimeters. Finally, a multifunctional organic optoelectronic diode of Glass / ITO / HTL (hole transport layer) / active layer / ETL (electron transport layer) / cathode metal is formed.

[0019] The thickness of the active layer film is 300 nanometers, the thickness of the electron transport layer is 10 nanometers, the thickness of the cathode is 120 nanometers, and the thickness of the hole transport layer is 10 nanometers.

[0020] Application of a Multifunctional Organic Vertical Diode Integrating Transient Optical Detection and Optical Synapse Functions in Contactless Heart Rate Detection and Image Recognition

[0021] The device prepared by the present invention has the following characteristics:

[0022] 1. By utilizing the different directions of photogenerated carriers under different polarities of applied bias voltages, the device in the present invention realizes a multifunctional organic vertical diode with a positive-down optical synapse function and a negative-down transient optical detection function, providing a new design idea for multifunctional organic integration electronics.

[0023] 2. When the device in the present invention is used as a photodetector under a negative bias voltage, it has the characteristics of low noise, high detectivity, large linear dynamic range, and fast response. When used for PPG testing, it can distinguish the heart rates in resting and moving states.

[0024] 3. When the device in the present invention is used as an optical synapse under a positive bias voltage, it has the characteristics of weak light response, long state retention time, and low energy consumption, realizing the simulation of the association learning of "quenching thirst by looking at plums" and image recognition based on the ANN network. When used for image recognition, it can obtain a recognition rate of more than 80%.

[0025] 4. The device manufacturing process of the present invention is simple and can be prepared by solution method, having important application prospects in neuromorphic computing and bionic vision.

[0026] 5. The device described in the present invention is used as a photodetector under a negative bias voltage, showing an extremely low dark current density of 8.55 nA / cm² at -2V, a specific detectivity exceeding 10 Jones in the wavelength range from 330 nm (ultraviolet) to 970 nm (near-infrared), a linear dynamic range of 188 dB at 915 nm and 179 dB at 450 nm. When used for PPG testing, it can distinguish the heartbeats at rest and during movement; when the device is used as an optical synapse under a positive bias voltage, it shows a long memory time and realizes the association learning of "quenching thirst by looking at plums" and high image recognition accuracy. The present invention realizes for the first time a multifunctional organic vertical diode integrating transient optical detection and optical synapse functions, and also realizes for the first time a two-terminal vertical optical synapse, providing effective space and weight savings for space-limited applications (including wearable devices, smartphones, and other portable consumer electronic products), and reducing energy consumption. -2 of 13 Jones, the linear dynamic range is 188 dB at 915 nm and 179 dB at 450 nm. When used for PPG testing, it can distinguish the heartbeats at rest and during movement; when the device is used as an optical synapse under a positive bias voltage, it shows a long memory time and realizes the association learning of "quenching thirst by looking at plums" and high image recognition accuracy. The present invention realizes for the first time a multifunctional organic vertical diode integrating transient optical detection and optical synapse functions, and also realizes for the first time a two-terminal vertical optical synapse, providing effective space and weight savings for space-limited applications (including wearable devices, smartphones, and other portable consumer electronic products), and reducing energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram showing the structure of the organic photodetector in Example 1 of the present invention.

[0028] Figure 2Schematic diagram showing the negative transient optical detection and positive photonic synaptic functions of the multifunctional organic vertical diode in Embodiment 1 of the present invention.

[0029] Figure 3 Schematic diagram showing the negative operation of the multifunctional organic vertical diode in Embodiment 1 of the present invention.

[0030] Figure 4 Schematic diagram showing the normalized detectivity curve of the multifunctional organic vertical diode used as a photodetector in the negative direction in Embodiment 1 of the present invention.

[0031] Figure 5 Schematic diagram showing the use of negative transient optical detection of the multifunctional organic vertical diode in Embodiment 1 of the present invention for heart rate monitoring.

[0032] Figure 6 Schematic diagram showing the negative operation of the multifunctional organic vertical diode in Embodiment 1 of the present invention.

[0033] Figure 7 Schematic diagram showing the positive photonic synapse of the multifunctional organic vertical diode in Embodiment 1 of the present invention.

[0034] Figure 8 Schematic diagram showing the use of the positive photonic synapse of the multifunctional organic vertical diode in Embodiment 1 of the present invention to simulate the associative learning behavior of imagining plums to quench thirst.

[0035] Figure 9 Schematic diagram showing the use of the positive photonic synapse of the multifunctional organic vertical diode in Embodiment 1 of the present invention for ANN-based image recognition. Detailed implementation manners

[0036] The technical solutions of the present invention will be further described in detail below through the accompanying drawings and embodiments. It should be noted that the following embodiments do not limit the protection scope of the present invention, and any improvements and changes made on the basis of the present invention are within the protection scope of the present invention.

[0037] A multifunctional organic vertical diode integrating transient optical detection and photonic synaptic functions, the device structure sequentially includes a substrate, an anode, a hole transport layer, an active layer, an electron transport layer, and a metal cathode.

[0038] The electron donor material of the active layer: poly[[4,8-bis[5-(2-ethylhexyl)-4-chloro-2-thienyl]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl]-2,5-thiophenediyl[5,7-bis(2-ethylhexyl)-4,8-dioxo-4H,8H-benzo[1,2-c:4,5-c']dithiophene-1,3-diyl]-2,5-thiophenediyl](PM7),

[0039] Or, poly(3-hexylthiophene-2,5-diyl) (P3HT), poly[2,6′]-4,8-bis(5-ethylhexyl)benzo[1,2-b;3,3-b]dithiophene{3-fluoro-2[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl})(PTB7-Th)

[0040] Or, poly[[4,8-bis[5-(2-ethylhexyl)-4-fluoro-2-thienyl]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl]-2,5-thiophenediyl[5,7-bis(2-ethylhexyl)-4,8-dioxo-4H,8H-benzo[1,2-c:4,5-c']dithiophene-1,3-diyl]-2,5-thiophenediyl](PM6), etc.

[0041] The electron acceptor material of the active layer is 3′H-cyclopropa[1,9][5,6]fullerene-C60-Ih-3′-butyl benzoate, 1-[3-(methoxycarbonyl)propyl]-1-phenyl-[6.6]C61 (PCBM), or IEICO-4F

[0042] Or 2,2'-[[[6,6,12,12-tetra(4-hexylphenyl)-6,12-dihydrodithieno[2,3-d:2',3'-d']-s-indaceno[1,2-b:5,6-b']dithiophene-2,8-diyl]bis[methylene(3-oxo-1h-indene-2,1(3h)-dimethylene)]]bis[propylamine](ITIC), or Y6, etc.,

[0043] The electron transport layer is PDINO, PDINN, C70, C60, etc.

[0044] Furthermore, the transparent substrate is glass or a flexible substrate.

[0045] Furthermore, the anode is ITO or a conductive organic polymer.

[0046] Furthermore, the hole transport layer is an organic P-type polymer material (such as poly(4-butyltriphenylamine) (poly-TPD), 3,4-ethylenedioxythiophene mixed with polystyrene sulfonate (PEDOT:PSS), etc.).

[0047] Furthermore, the electron transport layer is a water-alcohol soluble material (such as any one of [9,9-dioctylfluorene-9,9-bis(N,N-dimethylaminopropyl)fluorene] (PFN), bromo-[9,9-dioctylfluorene-9,9-bis(N,N-dimethylaminopropyl)fluorene] (PFN-Br), polyethoxyethyleneimine (PEIE), etc.).

[0048] Further, the metal cathode is Al, Ag, Au, etc.

[0049] On a glass substrate with ITO, a hole transport layer, an active layer, an electron transport layer, and a metal cathode are sequentially evaporated or spin-coated to obtain a multifunctional organic vertical diode.

[0050] Example 1

[0051] As Figure 1 shown, a multifunctional organic vertical diode, whose device structure sequentially includes a substrate 1, an anode 2, a hole transport layer 3, an active layer 4, an electron transport layer 5, and a cathode 6.

[0052] The substrate 1 is glass, the anode 2 is ITO, and the hole transport layer is an organic P-type polymer material (such as poly(4-butyltriphenylamine) (poly-TPD), 3,4-ethylenedioxythiophene blended with polystyrene sulfonate (PEDOT:PSS), etc.). The active layer 4 is a blend film of an organic P-type material P3HT and an organic n-type material PCBM (the donor-acceptor ratio is 1:1), or a blend film of an organic P-type material PTB7-Th and an organic n-type material IEICO-4F (the donor-acceptor ratio is 1:1.2), and other possible organic blend heterojunction structures, with a film thickness of 300 nanometers. The electron transport layer 5 is 3,3'-(1,3,8,10-tetraanthra[2,1,9-def:6,5,10-d'e'f']diisoquinoline-2,9(1H,3H,8H,10H)-diyl)bis(N,N-dimethylpropane-1-amine oxide) (PDINO), 2,9-bis(3-((3-(dimethylamino)propyl)amino)propyl)-3,3'-(1,3,8,10-tetraanthra[2,1,9-def:6,5,10-d'e'f']diisoquinoline) (PDINN), C70, C60, etc. The cathode 6 is metal aluminum, silver, etc., with a thickness of 120 nanometers.

[0053] The preparation method of a multifunctional organic vertical diode described in this example is as follows:

[0054] ⑴ The ITO conductive glass is sequentially cleaned with soapy water, deionized water, acetone, ethanol, and ultrasonic for 15 - 30 min, then dried with a nitrogen gun, and subsequently treated with ultraviolet ozone for 30 min to serve as the anode 2;

[0055] ⑵ Spin-coat the hole transport layer 3 on the anode 2;

[0056] ⑶ Spin-coat the active layer 4 composed of a bulk heterojunction mixed solution of an organic P-type material and an organic n-type material on the hole transport layer 3 at a suitable rotation speed;

[0057] ⑷ Spin-coat the electron transport layer 5 on the active layer 4 at an appropriate rotational speed; deposit the cathode metal by vacuum evaporation of a vapor deposition system for 100 nm. The overlapping part where the cathode metal intersects with the anode ITO is the effective area of the device, which is 0.04 square centimeters. Finally, a multifunctional organic optoelectronic diode of Glass / ITO / HTL (hole transport layer) / active layer / ETL (electron transport layer) / cathode metal is formed.

[0058] Appendix Figure 2 The different functions of the multifunctional organic vertical diode involved in this embodiment under different applied biases are given. Under forward bias, after turning on the light, the photocurrent slowly rises with the increase of illumination time. After turning off the light, the photocurrent slowly decays, which is similar to the process of a biological organism receiving a stimulus response. That is, the multifunctional organic vertical diode realizes the optical synaptic function under forward bias. Under reverse bias, after turning on the light, the photocurrent immediately rises to the maximum value and remains stable. After turning off the light, the photocurrent immediately decays to the initial position. That is, the multifunctional organic vertical diode realizes the transient light detection (photoelectric detector) function under reverse bias.

[0059] Example 2

[0060] Test for monitoring heart rate when the multifunctional organic vertical diode is used as a photodetector under reverse bias:

[0061] As Figure 3 shown, when the multifunctional organic vertical diode operates under reverse bias, the ITO is connected to the negative electrode and the metal cathode is connected to the positive electrode. Appendix Figure 4 gives the normalized detectivity curve of the multifunctional organic vertical diode used as a photodetector under reverse bias. It can be seen from the figure that the peak detectivity of the device at high frequency (1 KHz) can reach 4.58×10 12 Jones. The results obtained when the fabricated multifunctional organic vertical diode is used for transmissive PPG testing under reverse bias are as Figure 5 shown. The normal heart rate of the test subject is 84 beats per minute, and the heart rate after exercise is 108 beats per minute.

[0062] Example 3

[0063] Test for simulating the associative learning behavior of "thinking of plums to quench thirst" and image recognition when the multifunctional organic vertical diode is used as an optical synapse under reverse bias:

[0064] As Figure 6 shown, when the multifunctional organic vertical diode operates under reverse bias, the ITO is connected to the positive electrode and the metal cathode is connected to the negative electrode. Appendix Figure 7The paired-pulse facilitation (PPF) behavior of the device under forward bias is presented. Under two consecutive light stimulations, the photocurrent of the device in the latter stimulation is significantly larger than that in the former stimulation, which is similar to the process of the response of organisms to external stimuli (the second stimulation often elicits a stronger response). Attachment Figure 8 The device's simulation of the associative learning behavior of "imagining plums to quench thirst" is presented. For a person who has never tasted plums, the descriptions of plums by others are regarded as neutral stimuli and initially cannot cause the person's instinctive salivation. The taste of plums is regarded as an unconditioned stimulus to cause salivation, and salivation is regarded as an unconditioned response. Here, the light stimulation at 450 nm is regarded as the description of plums by others, that is, the neutral stimulus, and the light stimulation at 850 nm is regarded as the description of plums by others, that is, the unconditioned stimulus. After training by matching the unconditioned stimulus with the neutral stimulus, the neutral stimulus can also induce the unconditioned response. Attachment Figure 9 The schematic diagram of the device for ANN-based image recognition is presented. After more than a dozen image recognition trainings, the device can achieve an image recognition accuracy of over 80%.

Claims

1. A multifunctional organic vertical diode integrating transient light detection and opto - synaptic functions, characterized in that: The structure sequentially includes a substrate, an anode layer, a hole transport layer, an active layer, an electron transport layer, and a metal cathode; On the substrate, an anode layer is coated, and then the hole transport layer, the active layer, the electron transport layer, and the metal cathode are sequentially evaporated or spin-coated to obtain a multifunctional organic vertical diode; Under forward bias, the multifunctional organic vertical diode realizes the optical synaptic function, and under reverse bias, the multifunctional organic vertical diode realizes the transient optical detection function; The electron donor material of the active layer is PM7, PTB7-Th, P3HT or PM6; the electron acceptor material of the active layer is PCBM, IEICO-4F, ITIC or Y6.

2. The multifunctional organic vertical diode integrating transient optical detection and optical synaptic functions according to claim 1, wherein: The hole transport layer is poly-TPD or PEDOT:PSS.

3. The multifunctional organic vertical diode integrating transient optical detection and optical synaptic functions according to claim 1, wherein: The electron transport layer is a water-alcohol soluble material PFN, PFN-Br or PEIE.

4. The multifunctional organic vertical diode integrating transient optical detection and optical synapse functions according to claim 1, wherein: The metal cathode is Al, Ag or Au, and the anode is ITO or a conductive organic polymer.

5. The multifunctional organic vertical diode integrating transient optical detection and optical synaptic functions according to claim 1, characterized in that: The electron transport layer is PDINO, PDINN, C70 or C60.

6. The multifunctional organic vertical diode integrating transient optical detection and optical synaptic functions according to claim 1, characterized in that: The active layer is a blend system film of an organic p-type material P3HT and an organic n-type material PCBM, or a blend system film of an organic p-type material PTB7-Th and an organic n-type material IEICO-4F.

7. The multifunctional organic vertical diode integrating transient optical detection and optical synapse functions according to claim 1, characterized in that: The preparation method steps are as follows: ⑴ The substrate coated with the anode is sequentially cleaned with soapy water, deionized water, acetone, ethanol, and ultrasonically cleaned for 15-30 min, then dried with a nitrogen gun, and then treated with ultraviolet ozone for 30 min as the anode; ⑵ Spin-coat the hole transport layer on the anode; ⑶ Spin-coat the active layer composed of a bulk heterojunction mixed solution of an organic p-type material and an organic n-type material on the hole transport layer at a suitable rotation speed; ⑷ Spin-coat the electron transport layer on the active layer at a suitable rotation speed; Evaporate 100 nanometers of the cathode metal by the vacuum evaporation method of the vapor deposition system. The overlapping part where the cathode metal intersects with the anode ITO is the effective area of the device, which is 0.04 square centimeters. Finally, a multifunctional organic optoelectronic diode of Glass / ITO / HTL / active layer / ETL / cathode metal is formed.

8. The multifunctional organic vertical diode integrating transient optical detection and optical synapse functions according to claim 7, characterized in that: The thickness of the active layer film is 300 nanometers, the thickness of the electron transport layer film is 10 nanometers, the thickness of the cathode is 120 nanometers, and the thickness of the hole transport layer is 10 nanometers.

9. Application of the multifunctional organic vertical diode integrating transient optical detection and optical synaptic functions according to any one of claims 1-8 in non-contact heart rate detection or image recognition.

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