High-bias-resistance single photosensitive material organic photodetector and preparation method thereof

Abstract

The present application relates to the technical field of optoelectronic devices and organic semiconductor, in particular to a high bias-resistance single photosensitive material organic photodetector and a preparation method, and its technical key points are: using single-component organic thin film as single-component photosensitive unit, and connecting in series with light-light gain variable resistance unit; by using single-component photosensitive unit and light-light gain variable resistance unit in series structure, using the nonlinear impedance characteristics (high impedance in dark state, low impedance under illumination) of light-light gain variable resistance unit, the technical problems of traditional single-component organic photodetector, such as dark current surge under high bias and inability to withstand high reverse bias, are successfully solved, so that the dark current can still be maintained at 10 ‑7 A / cm² order of magnitude and not breakdown, while significantly improving the efficiency of exciton dissociation, achieving the highest external quantum efficiency of more than 55% and 10 12 Jones detectivity, with the effects of narrow-band spectral response and high sensitivity.

Description

Technical Field

[0001] This invention relates to the fields of optoelectronic devices and organic semiconductor technology, specifically to a high bias voltage withstand single-photosensitive material organic photodetector and its preparation method. Background Technology

[0002] Organic photodetectors (OPDs) have shown great application potential in fields such as biomedical imaging, wearable electronic devices, machine vision, and optical communication due to their lightweight, flexibility, ability to be processed in large-area solutions, and the ability to control the spectral response range through molecular design.

[0003] Currently, mainstream OPDs employ a bulk-heterojunction (BHJ) structure as the photoactive layer. The BHJ structure mixes electron donor (D) and electron acceptor (A) materials, utilizing the energy level shift at the D / A interface to drive exciton dissociation. However, although BHJ-OPDs have achieved performance comparable to inorganic detectors, their commercialization is limited by several inherent "multi-component" drawbacks:

[0004] First, morphological stability and process complexity: The performance of BHJs is highly dependent on the microscopic phase separation morphology of the donor-acceptor blend film. This nanoscale morphology is extremely sensitive to processing solvents, additives, and thermal annealing conditions, resulting in poor batch-to-batch repeatability of the devices. Furthermore, phase separation evolution is prone to occur during long-term operation, affecting stability. Second, unavoidable broadband absorption: In multi-component systems, the absorption spectra of the donor and acceptor often overlap, making it difficult to achieve narrowband detection. For applications requiring specific wavelength selectivity (such as biofluorescence detection), BHJ structures often require additional filters, increasing system complexity. Finally, deep-level trapped states: The complex D / A interface introduces a large amount of disorder and interface states, which not only increases the source of dark current but also becomes the center of nonradiative recombination of charge carriers, limiting the device's specific detectivity.

[0005] Therefore, single-component organic photodetectors are considered a highly promising alternative. Single-component organic photodetectors (SC-OPD) use only one organic semiconductor material as the photosensitive layer, which not only greatly simplifies the fabrication process and eliminates complex phase morphology control issues, but also enables intrinsic narrowband detection in specific regions through the absorption spectrum of a single molecule. If its performance bottlenecks can be overcome, SC-OPD will greatly promote the development of organic photoelectric materials in the field of photoelectric detection.

[0006] Despite the theoretical advantages of monocomponent OPDs, their performance has long lagged significantly behind BHJ devices in practical development. Firstly, organic semiconductors have low dielectric constants (Ɛr≈3~5), and photoexcitation-generated electron-hole pairs (excitons) are strongly bound by Coulomb attraction (binding energy Eb≈0.3~0.5 eV). In BHJs, the LUMO-LUMO or HOMO-HOMO energy level difference at the D / A interface provides the driving force to overcome this binding energy. However, in monocomponent materials, the lack of such a heterojunction means that excitons often undergo twin recombination before dissociation, resulting in extremely low photogenerated carrier yields. Simultaneously, traditional monocomponent materials (such as phthalocyanines, P3HT, etc.) exhibit negligible external quantum efficiency (EQE) under no or low electric fields. Even high-performance non-fullerene acceptors (NFAs) such as Y6, when used as monocomponent layers, have shown poor performance in early studies, mainly attributed to low charge generation efficiency. Recent studies on the physical mechanisms indicate that certain NFA materials with specific molecular structures (such as A-DA'DA type) (e.g., Y6 and IT-4F) actually possess the potential for single-component operation. The mechanism lies in the fact that these materials can form emissive charge-transfer excitonic (CTE) states extremely rapidly (<1 ps) in the solid state. Although these CTE states have lower binding energies than ordinary excitons, they still require a strong external electric field to effectively dissociate into free carriers. This leads to a fatal contradiction: to obtain high photocurrent, a high reverse bias voltage must be applied to utilize the field-assisted Frenkel-Poole emission effect to "forcefully" pull apart the CTE states, quench their emission, and extract charge. However, for organic thin films tens to hundreds of nanometers thick, applying a high voltage leads to severe external circuit carrier injection (from the electrodes), causing a significant increase in dark current (the dark current under bias voltage is often several orders of magnitude higher than at 0 V, and the higher the bias voltage, the greater the dark current). Especially for single-component layered circuits, the lack of a continuous nanotransmission network for donors and acceptors, coupled with an active layer thickness limited to approximately 30 nm, leads to a massive dark current, causing a sharp drop in specific detectivity (D*), and in severe cases, even breakdown. Therefore, existing single-component OPDs are trapped in a vicious cycle: extremely low quantum efficiency (undetectable signal) at 0 or low bias voltages, and large dark current (noise drowning out the signal) or even breakdown at high bias voltages. This is precisely the technical problem that this invention urgently needs to solve.

[0007] In summary, developing a photosensitive material that can maintain the advantages of simplicity and stability of single-component photosensitive materials, achieve high photocurrent (or high external quantum efficiency), and withstand high electric fields (while satisfying EQE improvement and avoiding significant increase in dark current or even direct device breakdown) is an urgent need in the current field. Summary of the Invention

[0008] To address the aforementioned shortcomings of existing technologies, this invention provides a high-bias-voltage-tolerant single-photosensitive organic photodetector and its fabrication method. This effectively solves the problem that existing single-component organic photodetectors, due to the lack of donor-acceptor heterojunctions, are unable to efficiently dissociate excitons, resulting in extremely low photoresponse at low bias voltages and failure to function properly at high bias voltages due to dark current surges or even breakdown.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] In a first aspect, the present invention provides a single-photosensitive material organic photodetector with high bias voltage tolerance, comprising a substrate, an anode, an electron transport-hole blocking layer, a single-component photosensitive unit, a connecting layer, an optical-optical gain-variable resistive unit, and a cathode, which are sequentially stacked. The optical-optical gain-variable resistive unit is composed of a hole transport layer, a light-emitting layer, and an electron transport layer.

[0011] The optical-optical gain variable resistor unit and the single-component photosensitive unit are connected in series through the connecting layer or a direct heterojunction interface.

[0012] The overall thin film stack thickness of the detector is less than 500 nm.

[0013] Furthermore, the substrate material is glass, the anode material is ITO, the sheet resistance is no more than 20 ohms, and the transmittance in the visible and near-infrared bands is greater than 85%.

[0014] Furthermore, the charge-connecting layer serves to block electron leakage to the anode while allowing photogenerated holes to be injected into the photo-optical gain-variable resistor unit.

[0015] Furthermore, the electron transport-hole blocking layer material is zinc oxide nanoparticles, and the thickness of the electron transport-hole blocking layer film is 40 nm.

[0016] Furthermore, the single-component photosensitive unit is a thin film composed of a single organic semiconductor material;

[0017] The thickness of the single-component photosensitive unit is less than 50 nm;

[0018] The single-component photosensitive unit is used to absorb the light to be measured and generate photogenerated carriers.

[0019] Furthermore, the thickness of the single-component photosensitive unit is 20 nm;

[0020] Furthermore, the molecular configuration of the single organic semiconductor material is planar or quasi-planar, and it is an ADA or A-DA'DA type non-fullerene acceptor;

[0021] The single organic semiconductor material is a non-fullerene acceptor material, selected from Y6, IT-4F or PYF-TO;

[0022] The quadrupole moment of the single organic semiconductor material along the π-π stacking direction is greater than 80 e. .

[0023] Furthermore, the connecting layer material is TAPC, and the thickness is 30 nm;

[0024] The connecting layer is used to block electrons from leaking to the anode, reducing dark current, while allowing photogenerated holes to be injected into the photo-optical gain variable resistor unit.

[0025] Furthermore, the optical-optical gain variable resistor unit is a wide-bandgap light-emitting diode structure, which is used to present high impedance in the dark state to suppress dark current, and to present low impedance due to carrier recombination and light emission in the illuminated state, so as to realize dynamic adjustment of the voltage division on the single-component photosensitive unit.

[0026] Furthermore, specifically, the optical-optical gain variable resistor unit is used to block carrier injection in the dark and reduce the voltage division on the single-component photosensitive unit with high impedance, while receiving photogenerated carriers from the single-component photosensitive unit under illumination to efficiently recombine and generate photocurrent, and reducing impedance to achieve high voltage gain for exciton dissociation and charge transport in the single-component photosensitive unit.

[0027] Furthermore, the constituent material of the hole transport layer is selected from one of TAPC, TCTA, TPD, NPB, Spiro-NPB, Spiro-TPD, m-MTDATA, CBP, or mCP;

[0028] The light-emitting layer is composed of a host-guest light-emitting system consisting of a host material and a guest material. The host material is a wide-bandgap host selected from CBP, m-CBP, CDBP, mcp, or DMIC-TRz. The guest material is selected from phosphorescent materials or thermally activated delayed fluorescence materials. The internal quantum efficiency of the constituent materials is close to 100%.

[0029] The electron transport layer is made of one of the following materials: TmPyPb or a double layer of PO-T2T / ANT-BIZ, B4PYMPB, B3PYMPM, B3PYPPM, TPBi, SPPO13, PO-T2T, or T2T.

[0030] Furthermore, the hole transport layer has a thickness of 10 nm to 20 nm, the light-emitting layer has a thickness of 20 nm to 40 nm, and the electron transport layer has a thickness of 30 nm to 60 nm.

[0031] Furthermore, the phosphorescent material is selected from one of Ir(ppy)3, Ir(piq)2(acac) or Ir(MDQ)2acac;

[0032] The thermally activated delayed fluorescence material is selected from 4CzIPN.

[0033] Furthermore, the constituent materials of the light-emitting layer are CBP:Ir(MDQ)2acac or DMIC-TRz:RD.

[0034] Furthermore, the overall structure of the detector can withstand a reverse bias voltage of -4 V to -10 V, and the dark current density remains at 10 V within the reverse bias voltage range. -7 A / cm 2 Within the order of magnitude, and the increase in dark current with bias voltage does not exceed two orders of magnitude.

[0035] In a second aspect, the present invention provides a method for fabricating a high bias voltage resistant single-photosensitive organic photodetector, the method being used to fabricate a high bias voltage resistant single-photosensitive organic photodetector as described in the first aspect, comprising the following steps:

[0036] Deposit an anode on a substrate;

[0037] An electron transport-hole blocking layer is deposited on the anode;

[0038] A single organic semiconductor material is dissolved in a solvent and spin-coated to form a single-component photosensitive unit with a thickness of less than 50 nm.

[0039] A bonding layer is deposited on the single-component photosensitive unit;

[0040] A light-to-light gain variable resistance unit thin film is prepared on the surface of the connecting layer;

[0041] A cathode film is deposited on the surface of the optical-optical gain-variable resistor unit to obtain an organic photodetector.

[0042] Furthermore, the electron injection layer is made of LiF and has a thickness of 1 nm.

[0043] Furthermore, the cathode is made of Al and has a thickness of 100 nm.

[0044] The technical solution provided by this invention has the following advantages compared with the known prior art:

[0045] 1. This invention employs a series structure of a single-component photosensitive unit and an optical-optical gain-variable resistor unit. Utilizing the nonlinear impedance characteristics of the optical-optical gain-variable resistor unit (high impedance in dark state, low impedance under illumination), it achieves stable operation of the device under high reverse bias voltages from -4 V to -10 V without breakdown. This successfully solves the technical problem of traditional single-component organic photodetectors exhibiting a surge in dark current and inability to withstand high reverse bias voltages under high bias voltages. In the dark state, the variable resistor unit exhibits high impedance, sharing most of the bias voltage and effectively blocking carrier injection, controlling the dark current density to within 10. -7 A / cm 2 The dark current is limited to within two orders of magnitude as the bias voltage increases, preventing device breakdown. Under illumination, the unit exhibits low impedance due to carrier recombination and luminescence, causing most of the high reverse bias voltage (e.g., -4 V to -10 V) to drop onto the single-component photosensitive unit. This dynamic voltage division mechanism not only ensures the stability of the device under high bias voltage, but also significantly promotes the dissociation of excitons and charge transport in the single-component material using a strong electric field, thereby greatly improving the device's photoresponsivity and external quantum efficiency (EQE) without sacrificing the signal-to-noise ratio.

[0046] 2. This invention controls the thickness of the single-component photosensitive unit to less than 50 nm, and combines it with a specific molecular configuration and quadrupole moment (Q). π >80e Non-fullerene acceptor materials (such as Y6, PYF-TO) and planar molecules (such as Y6, IT-4F, IDIC) have stronger intermolecular π-π stacking, which is conducive to the formation of delocalized electronic states. The high quadrupole moment induces a huge electrostatic potential difference at the grain boundaries of polycrystalline thin films. This microscopic potential difference provides a driving force similar to heterojunctions, which assists in exciton dissociation.

[0047] 3. This invention constructs an optical-optical gain-variable resistor unit by using phosphorescent materials or thermally activated delayed fluorescence (TADF) materials with an internal quantum efficiency (IQE) close to 100%, ensuring efficient recombination of photogenerated holes and injected electrons. This design enables the detector to achieve significant optical gain under high bias driving: at a bias voltage of -8 V, the device achieves an EQE of over 30% at 800 nm, and approximately 45% at -10 V; when using PYF-TO material, the EQE at 930 nm exceeds 55% at a bias voltage of -8 V, significantly breaking through the efficiency bottleneck of traditional single-component organic photodetectors. Attached Figure Description

[0048] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0049] Figure 1 This is a schematic diagram of the device structure proposed in this invention;

[0050] Figure 2 This is a schematic diagram of the device structure in Embodiment 1 of the present invention;

[0051] Figure 3 The EQE curve measured in Example 1 of this invention;

[0052] Figure 4 The response curve obtained by calculating the EQE measured in Example 1 of this invention;

[0053] Figure 5 The current density-voltage curve measured in Example 1 of this invention;

[0054] Figure 6 The detectivity curve calculated in Embodiment 1 of the present invention;

[0055] Figure 7 This is a schematic diagram of the device structure in Embodiment 2 of the present invention;

[0056] Figure 8 This is the EQE curve measured in Example 2 of the present invention. Detailed Implementation

[0057] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0058] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail. The terms “comprising,” “including,” “having,” “containing,” etc., as used herein are open-ended terms, meaning that they include but are not limited to. Unless the context clearly indicates otherwise, the expressions “a” and “an” as used herein include plural references. It should be noted that “first,” “second,” etc., are used merely for convenience of description and distinction and should not be construed as indicating or implying relative importance. The term “about” as used herein indicates a range of ±20% of the following numerical value. In some embodiments, the term “about” indicates a range of ±10% of the following numerical value. In some embodiments, the term “about” indicates a range of ±5% of the following numerical value. The invention is further described below with reference to embodiments.

[0059] Reference Figures 1 to 8 The device structure proposed in this invention is as follows: Figure 1 As shown, it typically consists of two units connected in series: a single-component photosensitive unit and a photo-optical gain-variable resistor unit, which are fabricated by connecting the two units in series at a direct heterojunction interface. The two units are connected in series through an intermediate connecting layer or a direct heterojunction interface. Specifically, the general structure is as follows: the front end is similar to the structure of a traditional OPD, consisting of an ITO transparent electrode / ZnO (electron transport layer); the single-component photosensitive unit uses a single-component organic thin film of a single photosensitive material to absorb light and generate photoexcitons.

[0060] Following this is a connecting layer responsible for regulating the interface morphology, energy level matching, and mobility (carrier balance) of the two series-connected units. This connecting layer primarily blocks electron leakage to the anode and allows photogenerated holes to be injected into the opto-optical gain-variable resistor unit, thereby effectively reducing the device's dark current and achieving energy level matching between the two units. Next, an opto-optical gain-variable resistor unit is connected in series. This unit is a wide-bandgap light-emitting diode (typically composed of a hole transport layer / light-emitting layer / electron transport layer, similar to an OLED structure), and its main functions and core mechanisms are as follows:

[0061] In the entire device, the optical-optical gain-variable resistor unit primarily functions electrically as a nonlinear impedance control unit or rectifier diode to dynamically adjust the voltage division on the single-component photosensitive unit. Specifically, in the dark state, the optical-optical gain-variable resistor unit typically exhibits a large impedance because even with external circuit injection of electrons, the lack of photon excitation in the single-component photosensitive unit prevents the generation of photogenerated holes and injected electrons to recombine and form a significant electrical loop. At this point, the optical-optical gain-variable resistor unit absorbs most of the bias voltage, thus significantly suppressing the device's dark current. Simultaneously, the multi-level energy structure of the optical-optical gain-variable resistor unit effectively blocks carrier injection from the electrodes into the photosensitive layer (especially the injection of dark electrons or dark holes, which is blocked by the multi-level and large carrier injection barrier), further contributing significantly to dark current suppression. These features allow us to apply voltages far exceeding those of ordinary photodetectors (e.g., -4 V to -10 V) across the entire detector without causing device breakdown or an exponential increase in dark current with the bias voltage.

[0062] On the other hand, when the entire device is excited by light, photogenerated carriers (e.g., holes) generated by the single-component photosensitive unit drift under a strong electric field and are injected into the back-end photo-optical gain-variable resistor unit. The injected carriers encounter electrons from the counter electrode in the composite layer. By selecting luminescent materials with high internal quantum efficiency (PLQY close to 100% or IQE close to 100%) (such as phosphorescent materials or TADF materials), almost every injected carrier can be converted into a photon, ensuring efficient utilization of the photogenerated carriers. Moreover, the light emission process itself changes the impedance characteristics of the photo-optical gain-variable resistor unit. The impedance decreases drastically during light emission, and the bias voltage is distributed across the single-component photosensitive unit. This strong electric field assists the single photosensitive material in effectively dissociating it into free carriers. This is a complementary photoelectric process, resulting in a huge photocurrent gain for the entire device, and the device response generates a high photocurrent.

[0063] Therefore, throughout the process, the optical-optical gain variable resistor unit dynamically adjusts the impedance characteristics of the series resistance of the entire detector under dark and illuminated conditions, especially the voltage division characteristics on the single-component photosensitive unit layer. This not only promotes the efficient utilization of photogenerated charges to generate current, but also effectively solves the problems of low light response, poor bias voltage tolerance, and large dark current of single-component photosensitive material detectors, which is of great significance.

[0064] Key material selection and physical parameter design rules:

[0065] This invention precisely defines the properties of the materials used to distinguish it from ordinary OPD. The material characteristics required to achieve high performance are listed in detail below:

[0066] Selection of Single-Component Photosensitive Materials: Based on quadrupole moment and CTE kinetics, not all organic semiconductors are suitable for single-component layering. This invention limits the following physicochemical properties of single-component photosensitive materials: In terms of molecular geometry, planar or quasi-planar molecular structures are preferred, especially ADA (Acceptor-Donor-Acceptor) or A-DA'DA type non-fullerene acceptors (NFAs). Planar molecules (such as Y6, IT-4F, IDIC) have stronger intermolecular π-π stacking, which is conducive to the formation of delocalized electronic states, and the molecule should have a high quadrupole moment (Q). π This is an extremely critical microscopic parameter. This patent requires the quadrupole moment Q of the photosensitive material along the π-π stacking direction. π At least greater than 80 e (e.g., Q of Y6 and IT-4F) π All >190 e This is because the high quadrupole moment induces a huge electrostatic potential difference at the grain boundaries of the polycrystalline thin film. This microscopic potential difference provides a driving force similar to that of a heterojunction, assisting exciton dissociation (but dependent on high bias voltage). Finally, the material should have the ability to rapidly (<1 ps) form an emissive intermolecular CTE state under photoexcitation, and the luminescence intensity of this CTE state should exhibit a significant field-dependent quenching characteristic. This ensures the physical basis for obtaining high EQE in single-component devices under high bias voltage.

[0067] Furthermore, the material selection for the optical-optical gain-variable resistor unit of this invention prioritizes ensuring efficient carrier conversion, adhering to 100% internal quantum efficiency, but requires simplification or optimization for the detector structure. Phosphorescent or thermally activated delayed fluorescence (TADF) material systems are preferred because they can utilize 100% excitons, which directly affects the device's photoelectric conversion efficiency and photoresponse current. Simultaneously, energy level matching must be ensured; the HOMO level of the optical-optical gain-variable resistor unit should form a stepped or ohmic contact (or be connected through an intermediate layer) with the HOMO level of the photosensitive layer to ensure excellent barrier injection of photogenerated holes. Finally, carrier balance must be ensured, requiring the introduction of an electron transport layer (ETL) and a hole blocking layer (HBL) to confine electrons and holes to recombine in specific regions, preventing carriers from directly passing through the device and forming leakage current. For example, CBP, TCTA, and TPBi can be selected as hole transport hosts, while Ir(ppy)3 (green phosphorescence), Ir(piq)2(acac) (red phosphorescence), and 4CzIPN (TADF green phosphorescence) with 100% internal quantum efficiency can be selected. Regarding the specific material selection for each layer of the optical-optical gain-variable resistor unit: the hole transport layer is composed of one of TAPC, TCTA, TPD, NPB, Spiro-NPB, Spiro-TPD, m-MTDATA, CBP, and mCP; the light-emitting layer is composed of a host-guest light-emitting system consisting of a host material and a guest material, wherein the host material is a wide-bandgap host selected from one of CBP, m-CBP, CDBP, mcp, or DMIC-TRz, and the guest material is selected from phosphorescent materials or thermally activated delayed fluorescence materials, and the internal quantum efficiency of the constituent materials is close to 100%; the electron transport layer is composed of one of TmPyPb or a bilayer PO-T2T / ANT-BIZ, B4PYMPB, B3PYMPM, B3PYPPM, TPBi, SPPO13, PO-T2T, and T2T.

[0068] Example 1

[0069] This embodiment details the physical structure and manufacturing process of the core optoelectronic device, which is crucial for achieving "low cost and high sensitivity." The device is built on a pre-cleaned ITO (indium tin oxide) glass substrate, with ITO serving as a transparent anode, allowing infrared light to enter while visible light transmits. The entire thin-film stack thickness is less than 500 nm, and the specific structure is as follows... Figure 2 As shown, from bottom to top, they are:

[0070] Substrate and Anode: The material is glass / ITO, with a sheet resistance of no more than 20 ohms and a transmittance of more than 85% in the visible and near-infrared bands.

[0071] Electron transport-hole blocking layer (ETL-HBL), typically made of zinc oxide nanoparticles, has a film thickness of about 40 nm. Its function is to smooth the ITO surface, optimize the work function, facilitate electron transport from the photosensitive layer to the cathode, and block undesirable holes injected by the external circuit.

[0072] The single-component photosensitive unit uses a single-component infrared photosensitive layer. The material is Y6, a photosensitive material that meets the requirements of this patent. It is dissolved in 10 mg / mL chloroform solvent and spin-coated at 2000 rpm in a glove box filled with nitrogen (oxygen content and water content ppm value are both less than 0.1). The film is approximately 20 nm thick and requires no post-treatment.

[0073] The connecting layer material is the commonly used TAPC, with a thickness of 30 nm. Its function is to block electron leakage to the anode (reducing dark current) while allowing photogenerated holes to pass smoothly through the injection-optical gain-variable resistor unit. TAPC is a commonly used hole transport material (HTM) in organic optoelectronics and also a high-performance electron blocking material. Its chemical name is 4,4'-(cyclohexane-1,1-diyl)bis(N,N-bis(4-methylphenyl)aniline), and its molecular formula can be represented as C1. 46 H 46 N2 is a classic organic semiconductor material used in devices such as OLEDs and organic photodetectors.

[0074] The optical-optical gain-variable resistor unit consists of a hole transport layer, an emissive layer, and an electron transport layer, with the hole transport layer (10-20 nm), the emissive layer (20-40 nm), and the electron transport layer (30-60 nm) being the three layers.

[0075] The photoelectric gain-variable resistor unit uses CBP:Ir(MDQ)2acac (8wt%) as its emitting layer material. Its function lies in the fact that the host-guest system of CBP:Ir(ppy)2acac ensures efficient energy transfer, and the highly efficient red phosphorescent dye Ir(MDQ)2acac can utilize triplet excitons, theoretically achieving a quantum efficiency of 100%. Photogenerated holes recombine with electrons injected from the cathode in this layer, allowing for highly efficient utilization of photogenerated holes. Simultaneously, the reduced impedance causes most of the bias voltage to drop onto the aforementioned single-component infrared photosensitive layer Y6 film. This high bias voltage drives exciton dissociation and charge transport, generating a large photocurrent.

[0076] The electron transport layer (ETL) assists in electron transport and facilitates electron injection into the optical gain variable resistor unit provided by the external circuit.

[0077] The electron injection layer (EIL) is made of LiF (lithium fluoride) and is approximately 1 nm thick. Its function is to significantly reduce the electron injection barrier of the aluminum cathode by utilizing the quantum tunneling effect, which is key to achieving low-voltage drive.

[0078] The cathode material is Al (aluminum), with a thickness of about 100 nm. Its function is to reflect light and provide electrons.

[0079] Key design parameters and verification include:

[0080] Thickness of single-component photosensitive unit: If the rotation speed is reduced at the same concentration, the thickness of the single-component infrared photosensitive unit will be significantly higher than 50 nm. In this case, no EQE response will be measured under sheet pressure. This is because the thicker film prolongs the lack of continuous nano-interchange network and charge transport channel in the single-component infrared photosensitive unit, which will cause non-radiative recombination. Therefore, the thickness of the single-component infrared photosensitive unit needs to be limited to below 50 nm.

[0081] When the photosensitive layer thickness in the single-component photosensitive unit is as described in Example 1 (approximately 20 nm), and the device is fabricated as in Example 1, a significant photoresponse is obtained under reverse bias, and the EQE and responsivity are measured and calculated (as shown in Example 1). Figure 3 and Figure 4 As shown in the figure, the device achieves an EQE of over 30% at 800 nm with a bias voltage of -8 V, and an EQE of approximately 45% with a bias voltage of -10 V. Moreover, the EQE response is strongly correlated with the applied bias voltage. More importantly, the EQE value in the EQE curve is correlated with the wavelength, which reflects the intrinsic absorption of Y6. This verifies the effectiveness of this invention in obtaining high EQE for single-photosensitive materials and its potential to detect specific wavelengths of characteristic absorption of single-component materials.

[0082] The present invention further tests and verifies the dark current of Embodiment 1, such as Figure 5 As shown, even at a relatively high bias voltage of -10 V, the dark current density of the device is still controlled at 10. -7 A / cm 2 The device exhibits excellent performance without breakdown within an order of magnitude range, while the increase in dark current density is limited to two orders of magnitude over a wide bias range from -1 V to -10 V. This verifies the significant high bias tolerance (up to -10 V operating bias range) and effective suppression of dark current under bias voltage of the photodetector designed in this invention.

[0083] The detector value of the device is calculated from the measured EQE value and dark current value, as follows: Figure 6 As shown. The photodetector in Example 1 achieves a detectivity of 10¹² Jones at 800 nm even with an applied voltage of -8 V, verifying that the present invention can realize a high-performance single-component photosensitive unit organic photodetector.

[0084] Example 2

[0085] The device structure in this embodiment is as follows: Figure 7 As shown, the difference from Example 1 is that:

[0086] The selected single-component photosensitive unit material is another photosensitive material PYF-TO that meets the requirements of this patent. It is dissolved in 10 mg / mL chloroform solvent and spin-coated into a film at 4000 rpm in a glove box filled with nitrogen (oxygen content and water content ppm value are both less than 0.1). (No post-treatment is required, and the thickness is about 20 nm.)

[0087] The connecting layer is made of a double layer of TAPC / TCTA with thicknesses of 30 nm and 10 nm, respectively. Its function is to block electron leakage to the anode (reducing dark current) while allowing photogenerated holes to pass smoothly through the injection-optical gain-variable resistor unit.

[0088] The photoelectric gain-variable resistor unit uses DMIC-TRz:RD (RD is a commercially available high-performance red phosphorescent material) (4 wt%) as its emitting layer material. The thickness is approximately 30 nm. Its function is to ensure efficient energy transfer through the host-guest system of DMIC-TRz:RD, and the highly efficient red phosphorescent dye RD can utilize triplet excitons, theoretically achieving a quantum efficiency of 100%. Photogenerated holes recombine with electrons injected from the cathode in this layer, allowing for highly efficient utilization of photogenerated holes. Simultaneously, the reduced impedance causes most of the bias voltage to drop onto the aforementioned single-component infrared photosensitive layer, the PYF-TO thin film. This high bias voltage drives exciton dissociation and charge transport, generating a large photocurrent.

[0089] The electron transport layer (ETL) is a bilayer PO-T2T / ANT-BIZ material with thicknesses of 10 nm and 30 nm, respectively. Its function is to assist electron transport, facilitating electron injection from the external circuitry into the optical gain-variable resistor unit.

[0090] The remaining layers are the same as in Example 1.

[0091] The key parameter tests and verifications performed in this embodiment include:

[0092] The photodetector device fabricated in Case 2 achieved a high EQE (e.g., under reverse bias) Figure 8 As shown in the figure, the device achieves a %EQE of over 55% at 930 nm at -8 V, further validating the effectiveness and importance of the present invention.

[0093] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the protection scope of the technical solutions of the embodiments of the present invention.

Claims

1. A single-photosensitive organic photodetector with high bias voltage tolerance, characterized in that, It includes a substrate, an anode, an electron transport-hole blocking layer, a single-component photosensitive unit, a connecting layer, an optical-optical gain variable resistance unit, and a cathode, which are stacked in sequence. The optical-optical gain variable resistance unit is composed of a hole transport layer, a light-emitting layer, and an electron transport layer. The optical-optical gain variable resistor unit and the single-component photosensitive unit are connected in series through the connecting layer or a direct heterojunction interface. The overall thin film stack thickness of the detector is less than 500 nm.

2. The high bias voltage withstand single-photosensitive material organic photodetector according to claim 1, characterized in that, The single-component photosensitive unit is a thin film composed of a single organic semiconductor material; The thickness of the single-component photosensitive unit is less than 50 nm; The single-component photosensitive unit is used to absorb the light to be measured and generate photogenerated carriers.

3. The high bias voltage withstand single-photosensitive material organic photodetector according to claim 2, characterized in that, The molecular configuration of the single organic semiconductor material is planar or quasi-planar, and it is an ADA or A-DA'DA type non-fullerene acceptor. The single organic semiconductor material is a non-fullerene acceptor material, selected from Y6, IT-4F or PYF-TO; The quadrupole moment of the single organic semiconductor material along the π-π stacking direction is greater than 80 e. .

4. The high bias voltage withstand single-photosensitive material organic photodetector according to claim 1, characterized in that, The connecting layer material is TAPC, and the thickness is 30 nm; The connecting layer is used to block electrons from leaking to the anode, reducing dark current, while allowing photogenerated holes to be injected into the photo-optical gain variable resistor unit.

5. A high bias voltage withstand single-photosensitive material organic photodetector according to claim 1, characterized in that, The optical-optical gain variable resistor unit is a wide-bandgap light-emitting diode structure, which is used to present high impedance in the dark state to suppress dark current, and to present low impedance due to carrier recombination and light emission in the illuminated state, so as to realize dynamic adjustment of the voltage division on the single-component photosensitive unit.

6. The high bias voltage withstand single-photosensitive material organic photodetector according to claim 5, characterized in that, The material used to construct the hole transport layer is selected from one of TAPC, TCTA, TPD, NPB, Spiro-NPB, Spiro-TPD, m-MTDATA, CBP, or mCP. The light-emitting layer is composed of a host-guest light-emitting system consisting of a host material and a guest material. The host material is a wide-bandgap host selected from CBP, m-CBP, CDBP, mcp, or DMIC-TRz. The guest material is selected from phosphorescent materials or thermally activated delayed fluorescence materials. The internal quantum efficiency of the constituent materials is close to 100%. The electron transport layer is made of one of the following materials: TmPyPb or a double layer of PO-T2T / ANT-BIZ, B4PYMPB, B3PYMPM, B3PYPPM, TPBi, SPPO13, PO-T2T, or T2T.

7. A high bias voltage withstand single-photosensitive material organic photodetector according to claim 6, characterized in that, The composition of the light-emitting layer is CBP:Ir(MDQ)2acac or DMIC-TRz:RD.

8. The high bias voltage withstand single-photosensitive material organic photodetector according to claim 1, characterized in that, The overall structure of the detector can withstand a reverse bias voltage of -4 V to -10 V, and the dark current density remains at 10 V within the reverse bias voltage range. -7 A / cm 2 Within the order of magnitude, and the increase in dark current with bias voltage does not exceed two orders of magnitude.

9. A method for fabricating a single-photosensitive organic photodetector with high bias voltage tolerance, characterized in that, The method for preparing a high bias voltage withstand single-photosensitive material organic photodetector as described in any one of claims 1 to 8 includes the following steps: Deposit an anode on a substrate; An electron transport-hole blocking layer is deposited on the anode; A single organic semiconductor material is dissolved in a solvent and spin-coated to form a single-component photosensitive unit with a thickness of less than 50 nm. A bonding layer is deposited on the single-component photosensitive unit; An optical-optical gain-variable resistive unit thin film is prepared on the surface of the connecting layer; A cathode film is deposited on the surface of the optical-optical gain variable resistor unit to obtain an organic photodetector.

10. The application of a high bias voltage resistant single-photosensitive material organic photodetector as described in any one of claims 1 to 8 in the fields of weak light detection, biological imaging, and narrowband optical communication.

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