A supermultiplier broadband response non-fullerene organic photodetector and its fabrication method

Abstract

This invention discloses a supermultiplier broadband-response non-fullerene organic photodetector and its fabrication method. The detector uses the polymer PBDB-T as the electron donor and the narrow-bandgap non-fullerene molecule Y11 as the electron acceptor, forming a bulk heterojunction as the photoactive layer. Through interface layer engineering and active layer ratio optimization, a trap-assisted tunneling photomultiplication mechanism is constructed, achieving an ultra-high gain photoresponse in the ultraviolet-visible-near-infrared broadband range. The detector of this invention achieves an external quantum efficiency exceeding 166,000% and a responsivity of 1218 A / W in the 910 nm near-infrared band at a low bias voltage of +3V. After introducing a MoO3 hole transport layer, the dark current of the device is significantly suppressed, and the maximum specific detectivity at 940 nm reaches 3.8 × 10⁻⁶. 13 Jones, with a detectivity exceeding 3×10⁻⁶ across all full-response bands. 13 Jones possesses extremely strong low-light detection capabilities.

Description

Technical Field

[0001] This invention belongs to the field of organic photodetector technology, specifically relating to multiplying near-infrared organic photodetectors, and more particularly to a supermultiplying broadband response organic photodetector based on the non-fullerene acceptor Y11 and its preparation method. Background Technology

[0002] Photodetectors are core optoelectronic devices that convert optical radiation signals into detectable electrical signals, and they have irreplaceable application value in fields such as optical communication, biomedical imaging, environmental monitoring, defense night vision, and consumer electronics. Among them, organic photodetectors (OPDs) have overcome the inherent limitations of traditional inorganic semiconductor detectors in terms of large-area fabrication cost, flexibility, and spectral customization capabilities due to their inherent characteristics such as the designability of organic semiconductor molecular structures, precise control of optical band gaps, low-temperature solution processing, intrinsic flexibility and stretchability, and excellent biocompatibility. They have become a research hotspot in the field of optoelectronics in recent years.

[0003] Multiplier organic photodetectors (PM-OPD, also known as gain-type organic photodetectors) are an important branch of the OPD field. Based on the trap-assisted charge tunneling injection mechanism, they achieve intrinsic amplification of photoelectric signals through single-photon induced multi-charge carrier cyclic transport. Their external quantum efficiency (EQE) can break through the theoretical limit of 100% of traditional photodiodes. They have unique advantages in scenarios such as weak light detection, single-photon imaging, and ultra-sensitive biosensing. Moreover, they do not require the high reverse bias voltage drive required by inorganic avalanche photodiodes, making them perfectly suited to the application requirements of flexible low-power electronic systems.

[0004] In 1994, Hiramoto's group first observed photomultiplication in organic thin films, formally proposing the interface trap-induced charge tunneling injection mechanism, thus opening the prelude to PM-OPD research (Hiramoto M, Imahigashi T, Yokoyama M. Photocurrent multiplication in organic pigment films[J]. Applied Physics Letters, 1994, 64(2): 187-189.). In 2015, Zhang's group constructed a polymer bulk heterojunction system doped with trace amounts of fullerene acceptors, achieving ultra-high external quantum efficiency and establishing a classic material system for PM-OPD (Li L, Zhang F, Wang J, et al. Achieving EQE of 16,700% in P3HT:PC71BM based photodetectors by trap-assisted photomultiplication[J]. Scientific Reports, 2015, 5(1): 9181.). However, fullerenes and their derivatives have an inherent defect of small absorption coefficients in the visible to near-infrared bands, which results in weak response and low gain of PM-OPD based on fullerene systems in the near-infrared band, failing to meet the core requirements of near-infrared detection.

[0005] In recent years, non-fullerene electron acceptor materials have been widely used in the field of organic optoelectronics due to their tunable optical bandgap, excellent near-infrared absorption characteristics, and energy level matching flexibility. They have also provided a new material platform for the performance breakthrough of PM-OPD. In 2020, Yang's research group constructed a PM-OPD device based on the non-fullerene acceptor Y6, achieving a high-gain response in the near-infrared band (Yang K, Wang J, Zhao Z, et al. Ultraviolet to near-infrared broadband organic photodetectors with photomultiplication[J].Organic Electronics, 2020, 83: 105739.). However, existing non-fullerene PM-OPDs still face many technical bottlenecks: First, the highest external quantum efficiency and responsivity of most devices are concentrated in the visible light band, while the gain performance in the near-infrared band drops significantly, making it difficult to achieve high-sensitivity detection of near-infrared weak light signals; Second, high gain often requires extremely high reverse bias driving, resulting in high device power consumption, which cannot be adapted to low-power wearable electronic systems; Third, it is difficult to achieve both high gain and low dark current, as the device dark current increases significantly under high multiplication effect, leading to a low specific detectivity and severely weakening the weak light detection capability; Fourth, the device response speed and bandwidth are insufficient, limiting its practical application in scenarios such as optical communication and dynamic physiological signal monitoring.

[0006] Therefore, developing a broadband response PM-OPD with low bias driving, ultra-high gain in the near-infrared band, low dark current, and high specific detectivity is a technical problem that urgently needs to be solved in this field, and it is of great significance to promoting the practical application and industrialization of organic photodetectors. Summary of the Invention

[0007] To address the shortcomings of existing multiplication-type organic photodetectors, such as weak near-infrared response, high driving bias voltage, large dark current, insufficient weak light detection capability, and difficulty in balancing gain and detection performance, this invention provides a supermultiplication-type broadband response non-fullerene organic photodetector. It achieves strong near-infrared absorption through a narrow-bandgap non-fullerene acceptor Y11, constructs an efficient trap-assisted tunneling multiplication mechanism through trace donor doping, and achieves a balance between high gain and low dark current through interface layer engineering. Ultimately, it achieves ultra-high external quantum efficiency, high responsivity, and ultra-high specific detectivity in the near-infrared band under low bias voltage.

[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: A supermultiplier broadband response non-fullerene organic photodetector has a layered stacked structure, comprising, from bottom to top, a substrate, a cathode, an electron transport layer, a photoactive layer, a hole transport layer, and an anode.

[0009] The substrate is any one of a rigid quartz substrate, a glass substrate, or a flexible PET or PI substrate.

[0010] The cathode is any one of ITO conductive glass, ITO flexible electrode, or Ag or Al metal cathode.

[0011] The electron transport layer is any one of ZnO, PDINO, PEIE, and TiO2, and the thickness of the electron transport layer is 20~80nm; preferably, the electron transport layer is ZnO and the thickness is 30~50nm.

[0012] The electron transport layer preferably uses ZnO with a deep HOMO level, which is as low as -7.6 eV. This effectively blocks photogenerated holes at the electron transport layer / photoactive layer interface, promoting hole accumulation and enhancing the local electric field, thus significantly improving tunneling injection efficiency and photomultiplication gain. The hole transport layer preferably uses MoO3 with a shallow LUMO level, which is -2.3 eV. This effectively blocks electron injection from the anode, significantly suppressing the device's dark current. While maintaining a reasonable gain, this significantly improves the device's specific detectivity and weak light detection capability.

[0013] The photoactive layer is a bulk heterojunction structure formed by electron donor PBDB-T and electron acceptor Y11, wherein the mass ratio of electron donor PBDB-T to electron acceptor Y11 is 0.01:1 to 0.1:1; preferably, the mass ratio is 0.03:1. The thickness of the photoactive layer is 100 to 500 nm, preferably 200 to 300 nm; the photoactive layer is prepared by solution processing, and the solvent used includes at least one of chloroform, chlorobenzene, toluene, and o-dichlorobenzene, and the total concentration of the photoactive layer precursor solution is 40 to 80 mg / mL.

[0014] The photoactive layer is the core functional layer, employing a bulk heterojunction structure formed by electron donor PBDB-T and electron acceptor Y11. Y11, as a narrow-bandgap non-fullerene acceptor, has an absorption edge up to 940 nm and exhibits strong broadband absorption in the 400–990 nm UV-Vis-NIR band, particularly in the 800–940 nm NIR band, fundamentally solving the problem of weak NIR absorption in traditional fullerene systems. PBDB-T, as a wide-bandgap polymer donor, has a highly matched energy level with Y11, with a HOMO energy difference of 0.35 eV and a LUMO energy difference of 0.4 eV, enabling efficient interfacial dissociation of photoexcitons. Simultaneously, trace amounts of PBDB-T dispersed within the Y11 bulk can form isolated hole traps, providing the core structural basis for trap-assisted tunneling multiplication.

[0015] The non-fullerene acceptor Y11 described in this invention is 2,2'-[(2Z,2'Z)-[(6,12,13-tris(2-ethylhexyl)-3,9-tetramonyl-12,13-dihydro-6H-thieno[2'',3'':4',5']thieno[2',3':4,5]pyrrolo[3,2-g]thieno[2',3':4,5]thieno[3,2-b][1,2,3]triazolo[4,5-e]indol-2,10-diyl)bis(methylene)]bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene)]dimalonitrile, with the following molecular structure:

[0016] The polymer donor PBDB-T described in this invention is poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo[1,2-b:4,5-b']dithiophene))-alternating-(1,3-bis(5-thiophene)-5,7-bis(2-ethylhexyl)benzo[1,2-c:4,5-c']dithiophene-4,8-dione)], with the following molecular structure:

[0017] n represents the degree of aggregation, and n is an integer from 1 to 10000; Preferably, n is an integer from 10 to 5000; more preferably, n is an integer from 50 to 2000.

[0018] The hole transport layer is any one of MoO3, PEDOT:PSS, PTAA, and TAPC, and the hole transport layer thickness is 5~30nm; preferably, the hole transport layer is MoO3 and the thickness is 8~15nm.

[0019] The anode is any one of Ag, Au, or Al metal electrodes.

[0020] The photomultiplication mechanism of this invention is as follows: Y11 absorbs incident photons and generates excitons, which dissociate into photogenerated electrons and photogenerated holes at the PBDB-T / Y11 donor-acceptor interface; under the action of a forward bias electric field, the photogenerated electrons migrate rapidly through the electron transport layer to the cathode and are collected; the photogenerated holes are captured by the hole traps formed by PBDB-T and continuously accumulate at the ZnO / photoactive layer interface, forming a strong local built-in electric field, which significantly reduces the electron tunneling injection barrier of the anode, allowing electrons in the external circuit to continuously and massively tunnel into the photoactive layer, realizing the cyclic transport of thousands of charge carriers induced by a single photon, and ultimately generating an ultra-high photomultiplication effect.

[0021] Furthermore, this invention also provides a method for fabricating the above-mentioned supermultiplier broadband response non-fullerene organic photodetector, which employs an all-solution method compatible with large-area and flexible fabrication, and includes the following steps: (1) Substrate pretreatment: The substrate with the cathode is cleaned, dried and plasma treated in sequence for later use; (2) Electron transport layer preparation: An electron transport layer is prepared on the cathode surface of the pretreated substrate by solution spin coating or vacuum evaporation, followed by annealing and curing; (3) Preparation of photoactive layer: Under the protection of inert gas, PBDB-T and Y11 are dissolved in an organic solvent at a preset mass ratio and stirred to obtain a precursor solution. The precursor solution is coated on the surface of the electron transport layer by a solution spin coating method to prepare a photoactive layer film, which is then annealed. (4) Hole transport layer preparation: Hole transport layer is prepared on the surface of photoactive layer by vacuum evaporation or solution spin coating. (5) Anode fabrication: Under vacuum conditions, a metal anode is deposited on the surface of the hole transport layer to complete the device fabrication; (6) Encapsulation: In an inert gas protective atmosphere, the device is encapsulated with UV-cured epoxy resin and a transparent cover glass to isolate water and oxygen and improve the environmental stability of the device.

[0022] Preferably, in step (1), the substrate is cleaned by ultrasonic cleaning with deionized water, acetone and isopropanol in sequence, with each ultrasonic cleaning lasting 10 to 20 minutes. After cleaning, the substrate is dried in an oven at 60 to 80 degrees Celsius. Before film formation, the substrate is treated with oxygen plasma for 1 to 3 minutes.

[0023] Preferably, in step (2), the electron transport layer is prepared by solution spin coating, with a spin coating speed of 2500~3500 rpm and a spin coating time of 60s. After spin coating, the layer is placed on a heating table at 140~160℃ for annealing for 20~40min.

[0024] Preferably, in step (3), PBDB-T and Y11 are weighed in an inert atmosphere of a nitrogen glove box at a mass ratio of 0.03:1, dissolved in chloroform solvent, and a precursor solution with a total concentration of 30~50mg / mL is prepared. The solution is stirred at room temperature for 12~24h until completely dissolved. The precursor solution is then spin-coated onto the surface of the electron transport layer at a speed of 1500~2500rpm for 60s using a spin-coating method. The solution is then annealed on a heating table at 80~120℃ for 8~12min to remove residual solvent and optimize the film morphology and phase separation structure.

[0025] Preferably, in step (4), the hole transport layer is prepared by vacuum evaporation, with a vacuum degree below 5×10⁻⁶. -4 Evaporation under Pa conditions.

[0026] This invention solves the core problems of traditional multiplication-type organic photodetectors, such as weak near-infrared response, high driving bias voltage, large dark current, and insufficient weak-light detection capability. The device can be fabricated using an all-solution method, which is simple to implement and compatible with flexible, large-area fabrication. It has broad application prospects in near-infrared optical communication, non-invasive biomedical monitoring, night vision imaging, and anti-counterfeiting identification. Compared with existing technologies, this invention has the following significant advantages: 1. Broadband spectral response and excellent near-infrared absorption: Using narrow-bandgap non-fullerene acceptor Y11 as the photoactive host material, the absorption edge can reach 940nm, achieving a broad spectral response across the entire UV-Vis-NIR band from 400 to 990nm. This completely solves the core problem of weak near-infrared absorption in traditional fullerene systems, perfectly meeting the application requirements of near-infrared detection.

[0027] 2. Ultra-high photoelectric gain and low driving bias: By constructing an efficient trap-assisted tunneling multiplication mechanism through micro-doping of PBDB-T donors, the external quantum efficiency in the 910nm near-infrared band exceeds 166,000% and the responsivity reaches 1218A / W under a low forward bias of +3V. This breaks through the theoretical limit of 100% EQE of traditional photodiodes. It does not require high reverse bias driving, greatly reducing device power consumption and making it suitable for low-power flexible electronic systems.

[0028] 3. High specific detectivity and superior low-light detection capability: By introducing a MoO3 hole blocking layer, the dark current of the device is effectively suppressed, achieving a detection efficiency of 3.8 × 10⁻⁶ at 940 nm while maintaining high gain. 13 Jones's ultra-high specific detectivity, with specific detectivity exceeding 3×10⁻⁶ across the entire response band. 13 Jones can achieve nW / cm 2 It achieves precise detection of extremely weak light signals, and its weak light detection performance is at the forefront of the industry.

[0029] 4. Adjustable performance, adaptable to multiple application scenarios: The device response speed is dynamically adjustable with the incident light intensity, within 2mW / cm². 2 With a rise time as low as 0.05ms under illumination and a -3dB response bandwidth covering 1~10kHz, it can be adapted to static high-sensitivity low-light detection scenarios as well as meet the needs of low-to-medium frequency dynamic detection such as near-infrared optical communication and dynamic physiological signal monitoring, making it suitable for a wide range of applications.

[0030] 5. Simple fabrication process and strong industrial compatibility: The core functional layers of the device can all be prepared by solution spin coating, without the need for complex high-vacuum deposition equipment. The process steps are simple, the raw material cost is low, and it is compatible with the fabrication of large-area and flexible substrates. It can be matched with existing printed electronics and roll-to-roll production processes and has the potential for large-scale industrial application. Attached Figure Description

[0031] Figure 1 shows the normalized absorption spectra of the non-fullerene acceptor Y11 and the polymer donor PBDB-T in this invention.

[0032] Figure 2 shows the external quantum efficiency (EQE) spectra of the device in the embodiment of the present invention under different bias voltages (a); and the specific detectivity (D) spectra under different bias voltages. (c) Comparison of EQE for devices with different electron transport layers; (d) Comparison of EQE for devices with different donor-acceptor mixing ratios.

[0033] Figure 3 shows (a) a comparison of dark current density of devices with different active layer concentrations in the embodiments of the present invention; (b) a graph showing the EQE variation of the devices under different bias voltages; (c) a comparison of specific detectivity of devices with different active layer concentrations; (d) a test graph of the -3dB bandwidth of the devices; (e) a test graph of the response time of the devices under different bias voltages; and (f) a graph showing the normalized frequency response curve of the devices.

[0034] Figure 4 shows the application verification diagram of the photodetector of the present invention in the field of near-infrared optical communication; wherein (a) is the emission spectrum of commercial NIR-LED; (b) is the test result diagram of near-infrared optical communication transmission bit signal; and (c) is the demonstration result diagram of near-infrared optical communication transmission image. Detailed Implementation

[0035] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. The following embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0036] Example 1: Hypermultiplying Organic Photodetector without Hole Transport Layer 1. Material preparation: The substrate is ITO conductive glass (1.5cm×1.5cm, sheet resistance 15Ω / sq), the electron donor is PBDB-T, the electron acceptor is Y11, the electron transport layer is ZnO nanoparticle dispersion, the anode material is metallic Ag, and the solvent is chloroform. All materials are commercially available and can be used directly without further purification.

[0037] 2. Preparation steps: (1) Substrate pretreatment: The ITO conductive glass substrate was ultrasonically cleaned in deionized water, acetone and isopropanol for 15 min each, and then placed in an oven at 70~80℃ overnight to dry. Before film formation, oxygen plasma treatment was performed for 2~3 min. (2) Preparation of electron transport layer: ZnO nanoparticle dispersion was spin-coated onto the surface of pretreated ITO substrate at a spin speed of 2000~3000 rpm for 60 s. After spin coating, the substrate was placed on a heating table at 140~160℃ for annealing for 20~40 min to obtain a ZnO electron transport layer with a thickness of 30~50 nm. (3) Preparation of photoactive layer: In a nitrogen glove box, PBDB-T and Y11 were weighed at mass ratios of 0.01:1, 0.03:1 and 0.1:1, dissolved in chloroform solvent to prepare a precursor solution with a total concentration of 30~50mg / mL. The solution was stirred at room temperature for 12~24h until completely dissolved. The precursor solution was spin-coated onto the surface of ZnO electron transport layer at a speed of 1500~2500rpm for 60s to obtain a photoactive layer film with a thickness of 200~300nm. The film was then annealed on a heating table at 100℃ for 8~12min. (4) Anode preparation: The substrate with the photoactive layer deposited is transferred into a vacuum evaporation chamber, and the vacuum level is lower than 5×10 - 4 Under the condition of Pa, a metal Ag anode with a thickness of 100 nm is vapor-deposited; (5) Encapsulation: In a nitrogen glove box, UV-cured epoxy resin is applied around the device, leaving a central photosensitive area. After covering with a transparent cover glass, the device is cured with a UV curing lamp for 10-12 minutes to complete the device encapsulation.

[0038] 3. Performance Testing: The devices fabricated in this embodiment still exhibit significant multiplication effects at donor-acceptor ratios ranging from 0.01:1 to 0.1:1. The device with a donor-acceptor ratio of 0.01:1 achieves an external quantum efficiency (EPE) of 11100% in the 910 nm near-infrared band, while the device with a donor-acceptor ratio of 0.1:1 achieves an EEP of 10800% in the same band. The preferred device, with a donor-acceptor ratio of 0.03:1, achieves an EEP of 166000% in the 910 nm near-infrared band under a +3V bias voltage, a responsivity of 1218 A / W, and an excitation threshold power density as low as 20 μW / cm². 2 At 2mW / cm 2 Under 852nm laser irradiation, the device has a rise time as low as 0.05ms and a -3dB response bandwidth of 8kHz, demonstrating excellent dynamic response capabilities.

[0039] Example 2: Hypermultiplying Organic Photodetector with MoO3 Hole Transport Layer 1. Material preparation: Same as in Example 1, except that MoO3 is added as the hole transport layer material.

[0040] 2. Preparation steps: Steps (1) to (3) are completely consistent with those in Example 1; (4) Hole transport layer preparation: The annealed photoactive layer substrate is transferred into a vacuum evaporation chamber, and the vacuum level is lower than 5×10⁻⁶. -4 Under the condition of Pa, a MoO3 hole transport layer with a thickness of 10 nm was deposited by vapor deposition; (5) Anode preparation: In a vacuum environment, a metal Ag anode with a thickness of 100 nm is deposited on the surface of the MoO3 hole transport layer; (6) Packaging: Same as step (5) in Example 1.

[0041] 3. Performance Testing: The device fabricated in this embodiment exhibits an external quantum efficiency of 5770% at 910 nm under a +3V bias voltage, a dark current density that is two orders of magnitude lower than that of Example 1, and a maximum specific detectivity of 3.8 × 10⁻⁶ at 940 nm. 13 Jones's detectivity exceeds 3×10⁻⁶ in the full-response band from 400 to 990 nm. 13 Jones possesses extremely strong low-light detection capabilities.

[0042] Example 3: Hypermultiplying Organic Photodetectors with Different Donor-Acceptor Ratios The only difference between this embodiment and embodiment 1 is that in step (3), the mass ratio of PBDB-T to Y11 is 1:1, and the rest of the preparation steps, material parameters and test conditions are completely consistent with those of embodiment 1.

[0043] Performance test results: The device fabricated in this embodiment has a maximum external quantum efficiency of 42% at 910nm under a bias voltage of +3V, and no significant photomultiplication effect was observed, which verifies that trace donor doping is an important condition for achieving ultra-high photoelectric gain in this invention.

[0044] Example 4: Hypermultiplying Organic Photodetectors with Different Electron Transport Layers The only difference between this embodiment and embodiment 1 is that in step (2), the electron transport layer is PDINO, the spin coating speed is 2000~3000rpm, the thickness is 30~50nm, the annealing temperature is 80~120℃, and the annealing time is 8~12min. The other preparation steps, material parameters and test conditions are completely consistent with those of embodiment 1.

[0045] Performance test results: The device fabricated in this embodiment has a maximum external quantum efficiency of 18000% at 910nm under a bias voltage of +3V. The photomultiplication effect is significantly weaker than that of the ZnO electron transport layer device, which verifies that ZnO with deep HOMO energy level is more conducive to hole interface accumulation and can significantly improve tunneling injection efficiency and photomultiplication gain.

[0046] The only difference between this embodiment and embodiment 1 is that in step (2), the electron transport layer is PDINO, the spin coating speed is 2000~3000rpm, the thickness is 30~50nm, the annealing temperature is 80~120℃, and the annealing time is 8~12min. The other preparation steps, material parameters and test conditions are completely consistent with those of embodiment 1.

[0047] Performance test results: The device fabricated in this embodiment has a maximum external quantum efficiency of 18000% at 910nm under a bias voltage of +3V. The photomultiplication effect is significantly weaker than that of the ZnO electron transport layer device, which verifies that ZnO with deep HOMO energy level is more conducive to hole interface accumulation and can significantly improve tunneling injection efficiency and photomultiplication gain.

[0048] Figure 1 shows the normalized absorption spectra of Y11 and PBDB-T in this invention; it can be seen that the absorption spectrum of Y11 extends to 1000 nm in the near-infrared band and complements the absorption spectrum of PBDB-T.

[0049] Figure 2 shows the external quantum efficiency (EQE) spectra of the device in the embodiment of the present invention under different bias voltages (a); and the specific detectivity (D) spectra under different bias voltages. (a) Spectrum; (b) Comparison of EQE for different electron transport layer devices; (c) Comparison of EQE for devices with different donor-acceptor mixing ratios of 0.03:1, 0.1:1, 0.01:1, and 1:1. It can be seen that in Figure (a), the higher the applied voltage, the higher the external quantum efficiency (EQE), with the highest applied bias voltage being +3V, at which point the highest EQE is 166000%; in Figure (b), the higher the applied voltage, the higher the specific detectivity (D). The higher the voltage, the higher the maximum applied bias voltage is +3V, at which point the maximum D is... It is 3.8 10 13 Jones; In Figure (c), the EQE efficiency of the deep electron transport layer ZnO is about one order of magnitude greater than that of the shallow electron transport layer PDION; Figure (d) shows that the preferred donor-acceptor ratios of 0.03:1, 0.1:1 and 0.01:1 have significant multiplication effects, while the donor-acceptor ratio of 1:1 has no multiplication effect.

[0050] Figure 3 shows (a) a comparison of dark current densities of devices with different active layer concentrations in the embodiments of the present invention; (b) a graph showing the EQE variation of the devices under different bias voltages; (c) a comparison of specific detectivity of devices with different active layer concentrations; (d) a test graph of the response time of the devices under different bias voltages; (e) a graph of the normalized frequency response curve of the devices; and (f) a test graph of the -3dB bandwidth of the devices. It can be seen that in Figure (a), the higher the concentration, the lower the dark current density, with the minimum dark current being 5. 10 -5 A / cm 2 Figure (b) shows the external quantum efficiency (EQE) at a suitable concentration, with the highest EQE being approximately 1. 10 5 %; the higher the concentration in Figure (c), the higher the specific detectivity D of the device. The higher the value, the higher the D. It is 1.1 10 13 Jones; Figure (d) shows the rise and fall times of the device under different light intensities, with the fastest rise time being 0.035ms and the fastest fall time being 0.033ms; Figure (e) shows the rise and fall times of the device under different applied voltages, with the fastest rise time being 4.2ms and the fastest fall time being 3.5ms; Figure (d) shows that the device has a -3dB bandwidth of 1.1kHz.

[0051] Example 5: Verification of the near-infrared optical communication application of the photodetector of the present invention Using the supermultiplier organic photodetector prepared in Example 1 as the near-infrared light signal receiver and a commercial 850nm NIR-LED as the transmitter, a near-infrared optical communication system was constructed. Figure 4 shows the application verification diagram of the photodetector of the present invention in the field of near-infrared optical communication; where (a) is the emission spectrum of the commercial NIR-LED; (b) is the test result diagram of the near-infrared optical communication bit signal transmission; and (c) is the demonstration result diagram of the near-infrared optical communication image transmission. It can be seen that the LED emission peak in Figure (a) is at 780nm; Figure (b) has good optical communication transmission effect with a bit error rate of less than 10. -6 Figure (c) shows a physical demonstration of optical communication, which has already demonstrated objective application value.

[0052] As shown in Figure 4, based on the STM32F103 microcontroller platform, stable serial transmission of 10 characters "M-OPD@SCUT" was achieved with a bit error rate of less than 10%. -6 Simultaneously, it completed the near-infrared light transmission and reconstruction of a 256×256 grayscale image, verifying the practical potential of the device of this invention in the field of near-infrared secure optical communication.

Claims

1. A super-multiplication type wide-band response non-fullerene organic photodetector, characterized in that, The detector has a layered stacked structure, which, from bottom to top, includes a substrate, a cathode, an electron transport layer, a photoactive layer, a hole transport layer, and an anode. The photoactive layer is a bulk heterojunction structure formed by an electron donor and an electron acceptor. The electron donor is PBDB-T, i.e., poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo[1,2-b:4,5-b']dithiophene))-alternating-(1,3-bis(5-thiophene)-5,7-bis(2-ethylhexyl)benzo[1,2-c:4,5-c']dithiophene-4,8-dione)]; the electron acceptor is Y11, i.e., 2,2'-[(2Z,2'Z)-[(6,12,13-tris(2-ethylhexyl)- 3,9-Ceco-12,13-dihydro-6H-thieno[2'',3'':4',5']thieno[2',3':4,5]pyrrolo[3,2-g]thieno[2',3':4,5]thieno[3,2-b][1,2,3]triazolo[4,5-e]indol-2,10-diyl)bis(methylene)]bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene)]dimalonitrile; the mass ratio of electron donor PBDB-T to electron acceptor Y11 is 0.01:1 to 0.1:

1. 2.The super-multiplication type wideband response non-fullerene organic photodetector according to claim 1, characterized in that, The substrate is any one of a rigid quartz substrate, a glass substrate, or a flexible PET or PI substrate; the cathode is any one of an ITO conductive glass, an ITO flexible electrode, or an Ag or Al metal cathode; the anode is any one of an Ag, Au, or Al metal electrode. 3.The super-multiplication type wideband response non-fullerene organic photodetector according to claim 1, characterized in that, The electron transport layer is any one of ZnO, PDINO, PEIE, and TiO2, and the thickness of the electron transport layer is 20~80nm.

4. The supermultiplier broadband response non-fullerene organic photodetector according to claim 1, characterized in that, The hole transport layer is any one of MoO3, PEDOT:PSS, PTAA, and TAPC, and the hole transport layer thickness is 5~30nm.

5. The supermultiplier broadband response non-fullerene organic photodetector according to claim 1, characterized in that, In the photoactive layer, the mass ratio of electron donor PBDB-T to electron acceptor Y11 is 0.03:

1. 6.The super-multiplication type wideband response non-fullerene organic photodetector according to claim 1, wherein, The thickness of the photoactive layer is 100~500nm.

7. The super-multiplication type wideband response non-fullerene organic photodetector according to claim 1, wherein, The detector has photoelectric response in the ultraviolet-visible-near infrared band of 400-990 nm under +3V bias voltage, the external quantum efficiency of 910 nm near infrared band is greater than or equal to 160000%, the responsivity is greater than or equal to 1200A / W, and the specific detectivity of the device at 940 nm is greater than or equal to 3.5*10 13 Jones, -3dB response bandwidth is 1-10kHz.

8. A method of fabricating a super-multiplying broadband response non-fullerene organic photodetector according to any one of claims 1-7, characterized in that, Includes the following steps: (1) Substrate pretreatment: The substrate with the cathode is sequentially cleaned, dried and plasma treated; (2) Electron transport layer preparation: An electron transport layer is prepared on the cathode surface of the pretreated substrate by solution spin coating or vacuum evaporation, followed by annealing and curing; (3) Preparation of photoactive layer: Under the protection of inert gas, PBDB-T and Y11 are dissolved in an organic solvent at a preset mass ratio and stirred to obtain a precursor solution. The precursor solution is coated on the surface of the electron transport layer by a solution spin coating method to prepare a photoactive layer film, which is then annealed. (4) Hole transport layer preparation: Hole transport layer is prepared on the surface of photoactive layer by vacuum evaporation or solution spin coating. (5) Anode fabrication: Under vacuum conditions, a metal anode is deposited on the surface of the hole transport layer to complete the device fabrication; (6) Encapsulation: In an inert gas protective atmosphere, the device is encapsulated with UV-cured epoxy resin and a transparent cover glass to isolate water and oxygen.

9. The production method according to claim 8, characterized by, In step (3), PBDB-T and Y11 are weighed in an inert atmosphere of a nitrogen glove box at a mass ratio of 0.01:1 to 0.1:1 and dissolved in chloroform solvent to prepare a precursor solution with a total concentration of 30 to 50 mg / mL. The solution is stirred at room temperature until completely dissolved. The precursor solution is then spin-coated onto the surface of the electron transport layer at a speed of 2500 to 3500 rpm using a spin-coating method. The solution is then annealed on a heating table at 80 to 120°C for 8 to 12 minutes to remove residual solvent and optimize the film morphology and phase separation structure.

10. The application of the supermultiplier broadband response nonfullerene organic photodetector according to any one of claims 1-7 in near-infrared optical communication, non-invasive biomedical monitoring, night vision imaging, and anti-counterfeiting identification.

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