Organic semiconductor material and organic field effect transistor

Abstract

The invention relates to the technical field of photosensitive sensing, and discloses an organic semiconductor material and an organic field effect transistor, the organic semiconductor material comprises a main body transmission material and a photosensitive doping material, the photosensitive doping material comprises a donor and an acceptor, the lowest unoccupied molecular orbital energy level of the main body transmission material is higher than the highest occupied molecular orbital energy level of a donor of the photosensitive doping material; the lowest unoccupied molecular orbital energy level of the main body transmission material is lower than the lowest unoccupied molecular orbital energy level of an acceptor of the photosensitive doped material; the highest occupied molecular orbital energy level of the host transport material is lower than the highest occupied molecular orbital energy level of the donor of the photosensitive doped material. The organic semiconductor material has a light negative response characteristic.

Description

Technical Field

[0001] This application relates to the field of photosensitive sensing technology, and specifically, to organic semiconductor materials and organic field effect transistors. Background Art

[0002] Organic field effect transistors (OFETs) have advantages such as simple regulation and monolithic integration. Photoelectric transistors based on OFETs have received extensive attention and a large amount of research investment. Under illumination conditions, most of the organic semiconductor materials used in OFETs can absorb light energy to generate electron-hole pairs. Under the action of the gate voltage or the drain voltage, the electron-hole pairs are separated, the channel carrier density increases, and the source-drain current rises, that is, a positive photoresponse characteristic is exhibited. A negative response phototransistor (NPT) refers to a transistor in which the source-drain current (IDS) between the source and drain electrodes anomalously decreases under illumination conditions (ultraviolet light, infrared light, etc.). NPTs can be used to prepare low-power and high-frequency response devices, and have broad application prospects in fields such as new optical logic circuits, mirror image optical conversion, and optically encrypted electrical signals, and are expected to expand the functions of traditional optoelectronic devices.

[0003] It should be noted that the above statements are only used to provide background technical information related to this application, and do not necessarily constitute prior art. Summary of the Invention

[0004] In the first aspect of this application, an organic semiconductor material is proposed, including: a host transport material and a photosensitive doping material. The photosensitive doping material includes a donor and an acceptor. Among them, the lowest unoccupied molecular orbital energy level of the host transport material is higher than the highest occupied molecular orbital energy level of the donor of the photosensitive doping material; the lowest unoccupied molecular orbital energy level of the host transport material is lower than the lowest unoccupied molecular orbital energy level of the acceptor of the photosensitive doping material; the highest occupied molecular orbital energy level of the host transport material is lower than the highest occupied molecular orbital energy level of the donor of the photosensitive doping material.

[0005] For the organic semiconductor material proposed in this application, by optimizing the energy level relationship between the host transport material and the photosensitive doping material, the photosensitive doping material can form a long-lived charge separation state. In the organic semiconductor material, charge transfer can occur between the photosensitive doping material and the host transport material, so that the organic semiconductor material has a negative photoresponse characteristic. The organic semiconductor material proposed in this application contains a bulk heterojunction, and the bulk heterojunction can increase the interfacial area of the heterojunction, reduce the hindrance of charge transfer caused by interfacial defects of the heterojunction, facilitate intermolecular charge transfer, and enhance the response characteristic. The processing method is simple and a single film formation can be adopted, effectively simplifying the preparation process.

[0006] In some embodiments, the lowest excited triplet state T1 energy level of the photosensitive doping material donor is higher than the lowest excited triplet state T1 energy level of the photosensitive doping material acceptor, and the lowest excited singlet state S1 energy level of the photosensitive doping material donor is higher than the lowest excited singlet state S1 energy level of the photosensitive doping material acceptor, so as to prevent the energy of the acceptor in the photosensitive doping material from being reversely transferred to the donor, which helps to form a long-lived charge separation state between the donor and the acceptor in the photosensitive doping material. The LUMO energy level of the host transport material is lower than the LUMO energy level of the acceptor in the photosensitive transport material, facilitating the main carriers in the host transport material, that is, electrons, to be captured by the radical cations generated by the charge separation state formed by the donor and the acceptor in the photosensitive doping material, realizing the light negative response characteristic.

[0007] In some embodiments, the host transport material includes at least one of the following compounds:

[0008]

[0009] The aforementioned host transport material has a high electron mobility, which is beneficial to improving the performance of the organic field effect transistor. At the same time, the energy level matches that of the photosensitive doping material, and charge transfer can be carried out to realize the light negative response behavior.

[0010] In some embodiments, the donor of the photosensitive doping material includes at least one of the following compounds:

[0011]

[0012] The energy level of the aforementioned photosensitive doping material matches that of the host transport material. The donor in the photosensitive doping material can be excited and effectively transport photo-generated electrons. At the same time, it forms a strong intermolecular interaction with the acceptor molecule, inhibits the non-radiative relaxation of triplet excitons, and conducts more efficient charge transfer with the host transport material. Moreover, the introduction of the photosensitive doping material can make the host transport material easier to form an oriented thin film, thus having better electrical properties.

[0013] In some embodiments, the acceptor of the photosensitive doping material includes at least one of the following compounds:

[0014]

[0015]

[0016] The acceptor in the photosensitive doping material has a strong spin-orbit coupling between the singlet excited state and the triplet excited state, which can generate abundant triplet excitons. Its molecule has good rigidity, can effectively limit molecular thermal motion and oxygen diffusion, reduce non-radiative transitions, and at the same time can form stable radical anions to realize a long-lived charge separation state.

[0017] In some embodiments, the mass ratio of the host transport material to the photosensitive dopant material is 1:(1 - 10). When the mass ratio of the host transport material to the photosensitive dopant material is within the foregoing range, the obtained photosensitive dopant material helps the host transport material form a film with more excellent orientation while maintaining the transport characteristics of the host transport material, enhancing the transport characteristics. At the same time, it is beneficial to generate a sufficient number of long-lived charge separation states in the photosensitive dopant material, effectively conduct charge transfer, and achieve good negative photoresponse behavior.

[0018] In some embodiments, the mass ratio of the donor of the photosensitive dopant material to the acceptor of the photosensitive dopant material is 1:(1 - 20). When the mass ratio of the donor of the photosensitive dopant material to the acceptor of the photosensitive dopant material is within the foregoing range, the donor can be excited under light illumination to generate sufficient photogenerated electrons and transfer them to the molecules of the acceptor. At the same time, it is beneficial to achieve long-range charge transfer between the molecules of the acceptor, further form stable radical anions, so that the donor and the acceptor in the photosensitive dopant material form long-lived charge separation states.

[0019] In the second aspect of the present application, an organic field-effect transistor is proposed, and the semiconductor layer of the organic field-effect transistor includes the organic semiconductor material proposed in the present application.

[0020] The organic field-effect transistor proposed in the present application has a relatively low preparation process difficulty, can retain and store the negative photoresponse state for a long time, and can meet the application requirements in fields such as photoelectric synapses and information encryption / decryption.

[0021] In some embodiments, the organic field-effect transistor proposed in the present application further includes: a substrate; a source electrode and a drain electrode, the source electrode and the drain electrode are spaced apart on one side of the substrate; the semiconductor layer is located on the side of the source electrode and the drain electrode away from the substrate, and the orthographic projections of the source electrode and the drain electrode on the substrate are located within the orthographic projection of the semiconductor layer on the substrate. Thus, the device structure of the organic field-effect transistor proposed in the present application is easy to manufacture by a wet preparation process, reducing the influence of high temperature during electrode evaporation on the organic semiconductor material. In addition, the organic field-effect transistor proposed in the present application is convenient for preparing large-area integrated devices, which is beneficial to industrial production and application.

[0022] In some embodiments, it further includes: a modification layer, the modification layer is located between the source electrode and the semiconductor layer, and / or, the modification layer is located between the drain electrode and the semiconductor layer, and the modification layer includes at least one of N-(2-hydroxyethyl)piperazine, N,N'-bis(2-hydroxyethyl)piperazine, and polyethyleneimine. Description of the Drawings

[0023] The above and / or additional aspects and advantages of the present application will become apparent and be readily understood from the description of the embodiments in conjunction with the following drawings, wherein:

[0024] Figure 1 (a) Schematic diagram of the principle of generating photoexcited carriers at the heterojunction interface; Figure 1 (b) Schematic diagram of the principle of generating photoexcited carriers in the p-type semiconductor;

[0025] Figure 2 (a) Schematic diagram of the first working principle of the defect trapping mechanism type NPT in the prior art for trapping carriers through gate bias;

[0026] Figure 2 (b) Schematic diagram of the recombination of photoexcited carriers with trapped charges and working carriers respectively;

[0027] Figure 3 (a) Schematic diagram of the second working principle of the defect trapping mechanism type NPT in the prior art for achieving carrier trapping through the action of light of the first wavelength;

[0028] Figure 3 (b) Schematic diagram of the recombination of the trapped charges released under the action of light of the second wavelength with the working carriers;

[0029] Figure 4 (a) Schematic diagram of the working principle of the charge tunneling mechanism NPT in the prior art for achieving a negative optical response by trapping holes through gate bias;

[0030] Figure 4 (b) Schematic diagram of achieving a negative optical response by trapping electrons through gate bias;

[0031] Figure 5 Including the energy level diagram of the host transport material, the photosensitizing dopant material, and the long-lived charge separation state energy level diagram in the organic semiconductor material proposed in the present application;

[0032] Figure 6 Schematic diagram of the energy level characteristics of the donor and acceptor of the photosensitizing dopant material in the organic semiconductor material proposed in the present application;

[0033] Figure 7 Schematic diagram of the stable acceptor radical anion energy level that can be formed by the acceptor of the photosensitizing dopant material in an embodiment of the present application;

[0034] Figure 8 Schematic diagram of the relative positions of the HOMO and LUMO energy levels of the host transport material and the HOMO and LUMO energy levels of the donor and acceptor in the photosensitizing dopant material in the organic semiconductor material proposed in the present application;

[0035] Figure 9(a) is a schematic structural diagram of a bottom-gate bottom-contact organic field-effect transistor in the organic field-effect transistor proposed in this application;

[0036] Figure 9 (b) is a schematic structural diagram of a top-gate bottom-contact organic field-effect transistor in the organic field-effect transistor proposed in this application;

[0037] Figure 9 (c) is a schematic structural diagram of a double-gate bottom-contact organic field-effect transistor in the organic field-effect transistor proposed in this application;

[0038] Figure 10 is a schematic structural diagram of an organic field-effect transistor including a modification layer in an embodiment of this application;

[0039] Figure 11 is a transfer characteristic curve graph of the organic field-effect transistor in Example 1 of this application under dark conditions and under 365 nm ultraviolet light irradiation with different powers;

[0040] Figure 12 are I-V curves of the organic field-effect transistor in Examples 2 - 4 of this application under dark conditions, under 365 nm ultraviolet light irradiation, and after turning off the ultraviolet light irradiation, etc.;

[0041] Figure 13 (a) is a transfer characteristic curve graph of the organic field-effect transistor in Comparative Example 1 of this application under dark conditions, under 365 nm ultraviolet light irradiation, and after removing the ultraviolet light;

[0042] Figure 13 (b) is an output characteristic curve graph of the organic field-effect transistor in Comparative Example 1 of this application under dark conditions, under 365 nm ultraviolet light irradiation, and after removing the ultraviolet light;

[0043] Figure 14 (a), Figure 14 (b), Figure 14 (c) are respectively transfer characteristic curve graphs of the organic field-effect transistor in Comparative Examples 2 - 4 of this application under dark conditions, under 365 nm ultraviolet light irradiation, and after removing the ultraviolet light;

[0044] Figure 15 Ultraviolet-visible absorption spectra of the host transport material P4FTVT-C32 thin film (a), the photosensitive doping material thin film PPT:DMFL-TPD (b), and the P4FTVT-C32 / PPT:DMFL-TPD organic semiconductor thin film (c) on a quartz substrate.

[0045] Figure 16 (a) is an atomic force microscope AFM image of the morphology of the P4FTVT-C32 film layer in the source-drain electrode ITO channel;

[0046] Figure 16 (b) is an atomic force microscope (AFM) image of the thickness of the P4FTVT-C32 film layer in the source-drain electrode ITO channel;

[0047] Figure 16 (c) is an atomic force microscope (AFM) image of the morphology of the P4FTVT-C32 film layer doped with PPT:DMFL-TPD in the source-drain electrode ITO channel;

[0048] Figure 16 (d) is an atomic force microscope (AFM) image of the thickness of the P4FTVT-C32 film layer doped with PPT:DMFL-TPD in the source-drain electrode ITO channel;

[0049] Figure 17 is a schematic diagram of the mechanism for constructing negative photoresponse using the organic semiconductor material proposed in this application;

[0050] Figure 18 (a) is a transfer characteristic curve of an organic field-effect transistor prepared with the host transport material PDBD-Se as the semiconductor layer in the dark, under 365 nm ultraviolet light irradiation, and after removing the ultraviolet light;

[0051] Figure 18 (b) is a transfer characteristic curve of the organic field-effect transistor prepared in Example 5 in the dark and under 365 nm ultraviolet light irradiation with different powers;

[0052] Figure 19 is a transfer characteristic curve of the organic field-effect transistor in Example 6 of this application in the dark and under 365 nm ultraviolet light irradiation with different powers;

[0053] Figure 20 is the application of the organic field-effect transistor prepared in Example 1 of this application in a synapse, and the inhibitory postsynaptic current (IPSC) characteristic curves of the organic field-effect transistor under one-pulse light illumination (a), two-pulse light illumination (b), different light intensities (c), and pulse times (d).

[0054] Explanation of reference numerals:

[0055] Substrate 1; Gate 2; Gate insulating layer 3; n-type semiconductor 4; p-type semiconductor 5; Source 6; Drain 7; Carrier capture layer 8; Tunneling layer 9; Semiconductor layer 10; Modifying layer 11; Working carrier hole 12; Working carrier electron 13; Electron trapped by the trap under gate bias 14; Hole trapped by the trap under gate bias 15; Photoinduced electron transition process 16; Bulk doping process 17; Carrier recombination process 18. Detailed implementation manners

[0056] Embodiments of the present application will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, but there may be cases where unnecessary details are omitted. For example, there may be cases where details of well-known matters are omitted and repeated descriptions of actually identical structures are omitted. This is to prevent the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the accompanying drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter recited in the claims.

[0057] Unless otherwise defined, all technical and scientific terms used in the present application have the same meaning as commonly understood by those skilled in the technical field to which the present application pertains; the terms used in the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application; unless otherwise stated, the numerical values of the various parameters mentioned in the present application can be measured by various commonly used measurement methods in the art (for example, they can be tested according to the methods given in the embodiments of the present application).

[0058] The terms "comprising" and "having" and any variations thereof in the description and claims of the present application are open-ended expressions, that is, they include the content specified in the present application but do not exclude other aspects.

[0059] In the description of the present application, all the numbers disclosed herein are approximate values, whether or not the words "about" or "approximately" are used. There may be a difference of less than 10% or a reasonable difference considered by those skilled in the art for each numerical value, such as a difference of 1%, 2%, 3%, 4%, or 5%.

[0060] The "range" disclosed in this application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this way can include or exclude the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5. In this application, unless otherwise specified, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where both a and b are real numbers. For example, the numerical range "0 - 5" represents that all real numbers between "0 - 5" are fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0061] If there is no special instruction, all embodiments and optional embodiments of this application can be combined with each other to form new technical solutions.

[0062] If there is no special instruction, all technical features and optional technical features of this application can be combined with each other to form new technical solutions.

[0063] NPTs in the related art include charge transfer type NPTs, defect trapping mechanism NPTs, and charge tunneling mechanism NPTs. Among them, the device structure of the charge transfer type NPT is as Figure 1 shown, and the semiconductor layer is mainly composed of a p - n heterojunction. After absorbing incident light, electron - hole pairs are generated; under the action of an external electric field formed by the gate voltage, the electron - hole pairs dissociate, and the photo - generated holes obtained by dissociation recombine with the electrons in the n - type semiconductor, or similarly, the photo - generated electrons recombine with the holes in the p - type semiconductor, thereby realizing the negative optical response characteristics. Referring to Figure 1 (a) shows the generation of photo - generated carriers at the heterojunction interface in NPT, Figure 1 (b) shows the generation of photo - generated carriers in the p - type semiconductor. The charge transfer type NPT can continuously adjust the semiconductor conductance state through the light signal intensity or the magnitude of the gate bias voltage.

[0064] The defect capture mechanism NPT, whose semiconductor layer includes nanostructured semiconductors, may include 0D, 1D, and 2D semiconductor materials. These semiconductor materials usually have intrinsic defects or introduced defects, which become sites for capturing carriers. Its working principle includes two types. The first working principle is that in a dark environment, the trapping sites capture carriers through the gate bias voltage, as shown in Figure 2 (a), and these carriers have the opposite sign to the main working carriers. Under illumination, photo-generated carriers (electrons and holes) are generated in the semiconductor material, as shown in Figure 2 (b). Among them, the photo-generated carriers with the same sign as the main working carriers recombine with the carriers with the opposite sign trapped by the trap, while the photo-generated carriers with the opposite sign to the main working carriers recombine with the main working carriers in the semiconductor layer, thereby reducing the concentration of working carriers in the semiconductor and making the device exhibit a negative response characteristic to light. The second working principle is that under the irradiation of a certain short-wavelength light, a carrier with the opposite sign to the main working carrier among the photo-generated carriers is trapped by the trap. At this time, as shown in Figure 3 (a), there are more working carriers in the semiconductor. Under the irradiation of light with another wavelength, as shown in Figure 3 (b), the trapped carriers absorb light energy and jump out of the trap, combine with the working carriers with the opposite polarity that play a major role, and the device exhibits a negative response characteristic to light due to the reduction of the working carrier concentration.

[0065] The charge tunneling mechanism NPT utilizes the non-volatile storage characteristics of floating-gate transistors. Its negative response behavior to light is mainly caused by the photo-generated carriers in the large energy gap layer (i.e., the carrier capture layer) and their spatial separation under the action of the electric field caused by the applied gate voltage. As shown in Figure 4 (a), under illumination, free electron-hole pairs are generated in the carrier capture layer. Under the action of the applied gate voltage, holes are captured, and at the same time, the photo-generated electrons tunnel through the tunneling layer under the action of the applied gate voltage and enter the p-type semiconductor to recombine with the main working carriers, holes, reducing the concentration of working carriers and exhibiting a negative response characteristic to light. As shown in Figure 4 (b), under illumination, free electron-hole pairs are generated in the carrier capture layer. Under the action of the applied gate voltage, electrons are captured, and at the same time, the photo-generated holes tunnel through the tunneling layer under the action of the applied gate voltage and enter the n-type semiconductor to recombine with the main working carriers, electrons, reducing the concentration of working carriers and exhibiting a negative response characteristic to light.

[0066] As can be seen from the above, most of the NPT negative light responses in the related technologies require the auxiliary action of the gate voltage. Even for the NPT that does not require the auxiliary action of the gate voltage, it also needs to first rely on the auxiliary action of one-time photoexcitation and then exhibit the negative response to light. The NPT in the related technologies limits the application of negative light response devices.

[0067] The present invention provides an organic semiconductor material that realizes a negative response to light by optimizing the gate voltage and the early auxiliary effect of photoexcitation. A device prepared using this organic semiconductor material can achieve long-term storage of negative photoresponse information.

[0068] In a first aspect of the present application, an organic semiconductor material is proposed, including: a host transport material and a photosensitive doping material. The photosensitive doping material includes a donor and an acceptor. Among them, the lowest unoccupied molecular orbital (LUMO) energy level of the host transport material is higher than the highest occupied molecular orbital (HOMO) energy level of the donor of the photosensitive doping material; the lowest unoccupied molecular orbital energy level of the host transport material is lower than the lowest unoccupied molecular orbital energy level of the acceptor of the photosensitive doping material; the highest occupied molecular orbital energy level of the host transport material is lower than the highest occupied molecular orbital energy level of the donor of the photosensitive doping material.

[0069] The organic semiconductor material proposed in the present application includes: a host transport material and a photosensitive doping material. The structural unit of the host transport material includes an organic small molecule or a polymer semiconductor material. The photosensitive doping material is an organic afterglow material composed of two components, a donor (D) and an acceptor (A). Refer to Figure 15 , it can be observed from the ultraviolet absorption spectrum that the photosensitive doping material and the host transport material have completed bulk doping, and there is no chemical change during the doping process. The energy levels of the host transport material, the donor, and the acceptor of the photosensitive doping material in the organic semiconductor material satisfy the foregoing description. Refer to Figure 8 , that is, the energy level structure satisfies: the LUMO energy level of the host transport material is higher than the HOMO energy level of the donor of the photosensitive doping material; the LUMO energy level of the host transport material is lower than the LUMO energy level of the acceptor of the photosensitive doping material; the HOMO energy level of the host transport material is lower than the HOMO energy level of the donor of the photosensitive doping material. Thus, it is beneficial for the carriers of the host transport material to transfer charges with the D-A system photosensitive doping material. Further, refer to Figure 17 , charge transfer can occur between the HOMO and LUMO energy levels of the host transport material and the donor and acceptor of the photosensitive doping material. Thus, this organic semiconductor material has the characteristic of negative photoresponse.

[0070] The photosensitive doping material is doped in the host transport material in the form of bulk doping, such as Figure 5As shown, under light irradiation, the photosensitive doped material can generate long-lived charge-separated states, which is conducive to charge transfer between the charge carriers of the host transport material in the organic semiconductor material and the carriers generated by the D-A photosensitive system. The radical anion in the photosensitive doped material has a long lifetime, and the cationic part forms hole doping of the host transport material, resulting in a decrease in the concentration of working charge carriers (electrons) that play a conductive role in the host transport material, reducing the output current of the organic semiconductor material and being conducive to improving the negative photoresponse characteristics of the organic semiconductor material.

[0071] By doping the photosensitive doped material into the host transport material in a bulk doping manner, the photosensitive doped material that forms long-lived charge-separated states can be utilized to retain and store the state of negative photoresponse for a long time. In addition, by combining donors and acceptors, the light wavelength of the photosensitive response of the photosensitive doped material can be adjusted, which is conducive to improving the information storage time and the optoelectronic conversion efficiency of the device when the organic semiconductor material is used as a device.

[0072] In some embodiments, the lowest excited triplet state T1 energy level of the donor of the photosensitive doped material is higher than the lowest excited triplet state T1 energy level of the acceptor of the photosensitive doped material, and the lowest excited singlet state S1 energy level of the donor of the photosensitive doped material is higher than the lowest excited singlet state S1 energy level of the acceptor of the photosensitive doped material.

[0073] When the donor and acceptor in the photosensitive doped material satisfy the aforementioned energy level relationship, referring to Figure 6 , it is conducive to charge transfer and transport in the D-A photosensitive system of the photosensitive doped material composed of donors and acceptors under light excitation and prevents the reverse transfer of energy from the acceptor to the donor.

[0074] In some embodiments, the host transport material includes at least one of the following compounds:

[0075]

[0076] The host transport material in the organic semiconductor material proposed in this application includes: Formula 1-1, that is, a diketopyrrolopyrrole (DPP)-based conjugated polymer poly[(E)-1,2-bis(3,4-difluorothiophene)ethylene-alt-3,6-dithiophene-N,N'-bis(2-tetradecyloctadecyl)-pyrrolo[3,4-c]pyrrole-1,4-dione] (diketopyrrolopyrrole-based conjugated polymer, P4FTVT-C32), and Formula 1-2, that is, a dithienopyrrolo[3,2-b]pyrrole-benzothiazole-dithienopyrrolo[3,2-b]pyrrole (DBD) and its selenium copolymer (PDBD-Se). Within the aforementioned range, the host transport material includes an n-type semiconductor material or a bipolar semiconductor material, and the main working charge carriers are electrons.

[0077] In some embodiments, the donor of the photosensitive doping material comprises at least one of the following compounds:

[0078]

[0079] Among the donors of the photosensitive doping materials proposed in this application, Formula 2-1 is 2,7-bis(3-methylphenyl)-9,9-dimethylfluorene (DMFL-TPD), Formula 2-2 is 2,7-bis-(N,N-diphenylamino)-9,9-dimethyl-9H-fluorene (DDF), Formula 2-3 is 4,4'-(9,9-dimethyl-9H-fluorene-2,7-diyl)bis(1,2,3,3a,4,8b-hexahydrocyclopenta[b]indole) (DDFy), and Formula 2-4 is N2,N2,N7,N7-tetrakis(4-methoxyphenyl)-9,9-dimethyl-9H-fluorene-2,7-diamine (DDF4o). When the donor of the photosensitive doping material is within the foregoing range, the donor has strong electron activity and can transport charge carriers.

[0080] In some embodiments, the acceptor of the photosensitive doping material comprises at least one of the following compounds:

[0081]

[0082] Among the acceptors of the photosensitive doping materials proposed in this application, Formula 3-1 is 2,8-bis(diphenylphosphino)dibenzothiophene (PPT), Formula 3-2 is triphenylphosphine (TPP), Formula 3-3 is (methylenebis(2,1-phenylene))bis(diphenylphosphine oxide) (MEDPPO), and Formula 3-4 is diphenyl(pyren-1-yl)phosphine oxide (DPPO). When the foregoing acceptor is adopted for the photosensitive doping material, strong intermolecular interaction can be formed between the donor and the acceptor, and non-radiative relaxation of photo-generated triplet excitons can be inhibited. As Figure 7 shown, the acceptor can form a stable radical anion to achieve intermolecular charge transport of the acceptor. Moreover, the acceptor has strong spin-orbit coupling between the singlet state and the triplet state and can generate abundant triplet excitons. The molecules of the foregoing acceptor have high triplet state energy and a rigid structure, can effectively limit molecular thermal motion and oxygen diffusion, and reduce non-radiative transition.

[0083] In some embodiments, the mass ratio of the host transport material to the photosensitive doping material is 1:(1 - 10).

[0084] In some embodiments, the mass ratio of the donor of the photosensitive doping material to the acceptor of the photosensitive doping material is 1:(1 - 20).

[0085] In a second aspect of the present application, the present application provides an organic field-effect transistor, and the semiconductor layer of the organic field-effect transistor comprises the organic semiconductor material provided by the present application.

[0086] The semiconductor layer of the organic field-effect transistor provided by the present application comprises the organic semiconductor material provided by the present application. This organic field-effect transistor includes a photo-negative-response n-type organic field-effect transistor. By using the photosensitive doping material that can form long-lived charge-separated states in the organic semiconductor material, it is beneficial to retain and store the photo-negative-response state for a relatively long time, integrating the photosensitive performance and information storage performance. Further, the organic field-effect transistor provided by the present application changes the transistor of the existing interfacial heterojunction technology, which has relatively high requirements for the thickness of the heterojunction film to achieve a photo-negative response, thereby improving the device structure and reducing the process difficulty of fabricating the organic field-effect transistor.

[0087] In some embodiments, the organic field-effect transistor provided by the present application further comprises: a substrate; a source electrode and a drain electrode, the source electrode and the drain electrode being disposed at intervals on one side of the substrate; the semiconductor layer being located on the side of the source electrode and the drain electrode away from the substrate, and the orthographic projections of the source electrode and the drain electrode on the substrate being located within the orthographic projection of the semiconductor layer on the substrate.

[0088] The organic field-effect transistor provided by the present application includes a bottom-contact transistor. Refer to Figure 9 , Figure 9 (a), Figure 9 (b), Figure 9 (c) are respectively schematic diagrams of the structures of a bottom-gate bottom-contact transistor, a top-gate bottom-contact transistor, and a double-gate bottom-contact transistor.

[0089] In some embodiments, referring to Figure 9 (a), the organic field-effect transistor can be a bottom-gate bottom-contact transistor. On the substrate 1, a gate electrode 2 and a gate insulating layer 3 are sequentially disposed, and the source electrode 6 and the drain electrode 7 are disposed at intervals on the gate insulating layer 3, and the semiconductor layer 10 is disposed on the surfaces of the source electrode 5 and the drain electrode 7.

[0090] In some embodiments, referring to Figure 9 (b), the organic field-effect transistor can be a top-gate bottom-contact transistor. The source electrode 6 and the drain electrode 7 are disposed at intervals on the substrate 1, the semiconductor layer 10 is disposed on the surfaces of the source electrode 6 and the drain electrode 7, a gate insulating layer 3 is disposed on the semiconductor layer 10, and a gate electrode 2 is disposed on the gate insulating layer 3.

[0091] In some embodiments, referring to Figure 9(c), the organic field-effect transistor can be a double-gate bottom-contact transistor. A gate 2 and a gate insulating layer 3 are sequentially arranged on a substrate 1. A source electrode 6 and a drain electrode 7 are arranged at intervals on the gate insulating layer 3. A semiconductor layer 10 is arranged on the surfaces of the source electrode 6 and the drain electrode 7. A gate insulating layer 3 and a gate 2 are sequentially arranged on the semiconductor layer 10.

[0092] When preparing the bottom-contact transistor, the process of preparing the source and drain electrodes is carried out first, and the process of depositing the semiconductor layer is carried out later. The design of the foregoing bottom-contact transistor structure can reduce the influence of heat radiation and solvent corrosion generated in production processes such as electrode preparation and lithography on the semiconductor layer in the organic field-effect transistor, which is beneficial to the improvement of the large-area uniformity of the semiconductor layer in the organic field-effect transistor, the overall product performance and stability of the organic field-effect transistor, and is also beneficial to the design and implementation of large-scale industrial production.

[0093] In some embodiments, it further includes: a modification layer, the modification layer is located between the source electrode and the semiconductor layer, and / or, the modification layer is located between the drain electrode and the semiconductor layer, and the modification layer includes at least one of N-(2-hydroxyethyl)piperazine, N,N'-bis(2-hydroxyethyl)piperazine, and polyethyleneimine.

[0094] Reference Figure 10 , the modification layer 11 is arranged on the surfaces of the source electrode 6 and the drain electrode 7 and is located between the source electrode 6, the drain electrode 7 and the semiconductor layer 10. The material of the modification layer within the foregoing range can reduce the surface work function of the source and drain electrodes. The material of the foregoing modification layer contains a tertiary amine or secondary amine modification material, which can generate an electric dipole moment on the electrode surface, making the energy levels of the organic semiconductor materials of the source and drain electrodes and the semiconductor layer more matched to achieve ohmic contact, which is beneficial to the movement of electrons to the semiconductor layer. Thus, the mobility and working current of the organic field-effect transistor can be significantly improved, the threshold voltage of the organic field-effect transistor can be reduced, and the working efficiency can be improved.

[0095] In some embodiments, the source electrode and the drain electrode include a transparent electrode, and the transparent electrode independently includes at least one of indium oxide, tin oxide, and indium tin oxide.

[0096] The foregoing transparent oxide is used as a transparent electrode, and the surface work function of the transparent oxide is between 3.5 eV and 4.7 eV, which can modify and regulate the work function of the source and drain electrodes. When a transparent substrate and a transparent electrode are used at the same time, light can enter the organic field-effect transistor from the substrate direction, which is beneficial to more light contacting the organic field-effect transistor and can improve the photosensitive efficiency of the organic field-effect transistor. In addition, the processing process of the transparent electrode can be matched with the currently operating large-scale integrated circuit process, which is beneficial to the mass production and integration of the organic field-effect transistor proposed in the present invention.

[0097] In some embodiments, the organic field-effect transistor can be used as a basic unit for mimicking a neuromorphic synapse.

[0098] Reference Figure 20 , Figure 20 is the characteristic curve of inhibitory postsynaptic current (IPSC) of the organic field-effect transistor proposed in this application under single-pulse illumination (a), double-pulse illumination (b), different light intensities (c), and pulse durations (d). It can be seen from the figure that the organic field-effect transistor, as a light-negative response device, responds to both the pulse illumination time and the light intensity. Within a certain range, the negative response intensity increases with the increase of the pulse duration and the light intensity.

[0099] The solutions of the present application will be described below through specific embodiments. It should be noted that the following embodiments are only for illustrating the present application and should not be construed as limiting the scope of the present application. For those without specific techniques or conditions noted in the embodiments, the techniques or conditions described in the literature in this field or according to the product specifications are followed. For reagents or instruments without the manufacturer noted, they are all conventional products that can be obtained through commercial purchase.

[0100] Example 1

[0101] First step: Prepare the substrate of the bottom-gate bottom-contact organic field-effect transistor

[0102] Magnetron sputter 250 nm of metal Mo on a transparent glass substrate as the gate; chemically deposit an inorganic insulating layer SiO2 on the gate Mo as the gate insulating layer, and the thickness of the gate insulating layer is 300 nm; sputter 66 nm of indium tin oxide (ITO) on the SiO2 gate insulating layer as the source-drain electrodes; each layer needs to go through the steps of spin-coating, pre-baking, exposure, post-baking, development, etching, and stripping to achieve patterning.

[0103] Second step: Ultrasonically clean the substrate prepared in the first step with deionized water, acetone, and isopropyl alcohol for 10 min respectively, take it out and dry it with N2 to remove the solvent on the surface of the substrate.

[0104] Third step: Modify the ITO source-drain electrodes with ethoxylated polyethyleneimine (PEIE) (CAS: 26658-46-8). Dissolve PEIE in methoxyethanol, and the solution concentration is 0.08 wt%. Spin-coat the PEIE solution on the cleaned and dried substrate prepared in the second step, the spin-coating time is 30 s, and the spin-coating speed is 4000 rpm; after spin-coating, anneal on a hot plate at 100 °C for 10 min to remove the organic solvent and prepare the modification layer.

[0105] Fourth step: Dissolve the host transport material P4FTVT-C32 in 1,2-dichlorobenzene, and the concentration is 4 mg / mL to obtain the host transport material solution.

[0106] Step 5: Dissolve 2,8-bis(diphenylphosphoryl)dibenzothiophene (PPT) and 2,7-bis(3-methylphenyl)-9,9-dimethylfluorene (DMFL-TPD) in chloroform respectively to prepare PPT solution with a concentration of 20 mg / mL and DMFL-TPD solution with a concentration of 4 mg / mL. Then mix the solutions according to the mass ratio of PPT:DMFL-TPD = 5:1 to obtain a photosensitive doping material solution.

[0107] Step 6: Mix the host transport material solution (P4FTVT-C32 solution) obtained in Step 4 and the photosensitive doping material solution obtained in Step 5 according to a volume ratio of 1:1 to obtain an organic semiconductor material solution.

[0108] Step 7: Coat the organic semiconductor material solution obtained in Step 6 on the substrate obtained in Step 3 by using a wire bar coating method, with a coating speed of 60 mm / s and the temperature of the coating machine platform controlled at 20 °C (room temperature).

[0109] Step 8: Place the substrate prepared in Step 7 on a hot stage at 150 °C in a nitrogen atmosphere and anneal for 10 min to obtain an organic field effect transistor.

[0110] Example 2

[0111] Example 2 is consistent with Example 1, except that the concentration of the DMFL-TPD solution prepared in Step 5 is 0.6 mg / mL.

[0112] Example 3

[0113] Example 3 is consistent with Example 1, except that the concentration of the DMFL-TPD solution prepared in Step 5 is 2 mg / mL.

[0114] Example 4

[0115] Example 4 is consistent with Example 1, except that the concentration of the DMFL-TPD solution prepared in Step 5 is 10 mg / mL.

[0116] Example 5

[0117] Example 5 is consistent with Example 1, except that in Step 4, the host transport material solution is prepared by dissolving the host transport material PDBD-Se in 1,2-dichlorobenzene with a concentration of 10 mg / mL.

[0118] Example 6

[0119] Example 6 is consistent with Example 1, except that in the fifth step, a photosensitive doping material solution is prepared: PPT and DDF are respectively dissolved in chloroform to prepare a 20 mg / mL PPT solution and a 4 mg / mL DDF solution, and the solutions are mixed according to a mass ratio of PPT:DDF = 5:1.

[0120] Comparative Example 1

[0121] Comparative Example 1 is consistent with Example 1, except that in the fifth step, the preparation of the photosensitive doping material solution is omitted, and the host transport material solution prepared in the fourth step will be used as the organic semiconductor material solution in the sixth step.

[0122] Comparative Example 2

[0123] Comparative Example 2 is consistent with Example 1, except that in the fifth step, a photosensitive doping material solution is prepared: PPT (acceptor) is dissolved in chloroform at a concentration of 20 mg / mL.

[0124] Comparative Example 3

[0125] Comparative Example 3 is consistent with Example 1, except that in the fifth step, a photosensitive doping material solution is prepared: DMFL-TPD (donor) is dissolved in chloroform at a concentration of 4 mg / mL.

[0126] Comparative Example 4

[0127] Comparative Example 4 is consistent with Example 1, except that in the fifth step, a photosensitive doping material solution is prepared: DDF (donor) is dissolved in chloroform at a concentration of 4 mg / mL.

[0128] Testing method:

[0129] 1. UV-Vis spectrophotometric test

[0130] Tested using an Agilent 8453 UV-Vis spectrometer. During the test, a transparent quartz substrate is first used as a control to scan the curve, and after subtracting the blank background, the absorption curve of the sample is tested.

[0131] 2. Transfer and output characteristic curve (transistor I-V curve) test

[0132] Tested using a Keysight B1500A semiconductor device parameter analyzer. The test is carried out in a nitrogen environment. For the transfer characteristic curve, the source-drain voltage is set as a constant, and the curve of the current changing with the gate voltage is tested; for the output curve, at different fixed gate voltages, the curve of the current changing with the source-drain voltage is tested. After setting the scanning program and fixing the probe position, the electrical curves are scanned multiple times under different conditions (UV illumination / darkness).

[0133] Test results:

[0134] For the transfer characteristic curve of the organic field-effect transistor in Example 1, see Figure 11 . As can be seen from the figure, the negative photoresponse phenomenon of the organic field-effect transistor in Example 1 is obvious. When V GS = 80 V and the optical power is 246 μW / cm 2 , the current reduction is greater than 10 4 orders of magnitude, and the optical power can modulate the magnitude of the negative response.

[0135] For the I-V curves of the organic field-effect transistors in Examples 2 - 4, see Figure 12 . As can be seen from the figure, the I-V curve diagrams under dark (Drak), 365 nm ultraviolet light (UV on) irradiation, and after turning off the ultraviolet light irradiation (UV off) (V GS = 80 V, optical power is 246 μW / cm 2 ). The mass ratios of the acceptor and donor in the photosensitive doping material are 100:3, 100:10, 100:20, and 100:50 respectively, and the corresponding I-V curves of the devices are a - d. As can be seen from the figure and Comparative Examples 1, 2, and 3, when the ratio of the photosensitive doping material is in the range of 100:10 - 100:50, it has good negative photoresponse characteristics.

[0136] For the transfer characteristic curve of the organic field-effect transistor in Comparative Example 1, see Figure 13 (a), and for the output characteristic curve, see Figure 13 (b). As can be seen from the figure, the organic field-effect transistor that only contains the host transport material as the semiconductor layer has no negative photoresponse characteristics to light.

[0137] For the transfer characteristic curves of the organic field-effect transistors in Comparative Examples 2 - 4, see Figure 14 (a), Figure 14 (b), Figure 14 (c) respectively. As can be seen from the figure, for the organic field-effect transistor in Comparative Example 2 that only has PPT (acceptor) and the host transport material as the semiconductor layer, it has almost no negative photoresponse characteristics to light; for the organic field-effect transistor in Comparative Example 3 that only has DMFL-TPD (donor) and the host transport material as the semiconductor layer, it has negative photoresponse characteristics to light, but the effect is relatively small; for the organic field-effect transistor in Comparative Example 4 that only has DDF (donor) and the host transport material as the semiconductor layer, it has negative photoresponse characteristics to light, but the effect ratio is relatively small.

[0138] From Figure 18 (a) and Figure 18(b) By comparison, it can be seen that in Example 5, compared with the case where only the host transport material PDBD-Se is used as the semiconductor layer, the organic field-effect transistor hardly has a negative response to light. However, when the photosensitive doping material formed by the PPT acceptor and the DMFL-TPD donor is bulk-doped into the host transport material PDBD-Se, the resulting organic field-effect transistor shows an obvious negative light response characteristic. When V GS = 80 V and the optical power is 246 μW / cm 2 , the current reduction is greater than 10 4 orders of magnitude, and the optical power can modulate the magnitude of the negative response.

[0139] From Figure 19 it can be seen that in Example 6, the organic field-effect transistor shows an obvious negative light response characteristic. When V GS = 80 V and the optical power is 246 μW / cm 2 , the current is reduced by 10 5 orders of magnitude, and the optical power can modulate the magnitude of the negative light response.

[0140] From Figure 16 it can be seen that the organic semiconductor material proposed in this application has good processability, and a fibrous film layer can be formed by the blade coating method.

[0141] It should be noted that this application is not limited to the above embodiments. The above embodiments are only examples, and embodiments having the same constitution and the same function and effect as the technical idea within the technical solution scope of this application are all included in the technical scope of this application. In addition, within the scope not departing from the gist of this application, various modifications that can be thought of by those skilled in the art to the embodiments, and other ways constructed by combining some constituent elements of the embodiments are also included in the scope of this application.

Claims

1. An organic semiconductor material, characterized in that include: A host transmission material and a photosensitive doping material, wherein the photosensitive doping material includes a donor and an acceptor, wherein: The lowest unoccupied molecular orbital energy level of the host transport material is higher than the highest occupied molecular orbital energy level of the donor of the photosensitive dopant material; The lowest unoccupied molecular orbital energy level of the host transport material is lower than the lowest unoccupied molecular orbital energy level of the acceptor of the photosensitive doping material; The highest occupied molecular orbital energy level of the host transport material is lower than the highest occupied molecular orbital energy level of the donor of the photosensitive doping material.

2. The organic semiconductor material according to claim 1, characterized in that The lowest excited triplet state T1 energy level of the donor of the photosensitive doping material is higher than the lowest excited triplet state T1 energy level of the acceptor of the photosensitive doping material, and the lowest excited singlet state S1 energy level of the donor of the photosensitive doping material is higher than the lowest excited singlet state S1 energy level of the acceptor of the photosensitive doping material.

3. The organic semiconductor material according to claim 1, characterized in that The host transport material comprises at least one of the following compounds:

4. The organic semiconductor material according to claim 1, characterized in that The donor of the photosensitive doping material includes at least one of the following compounds:

5. The organic semiconductor material according to claim 1, characterized in that The acceptor of the photosensitive doping material comprises at least one of the following compounds:

6. The organic semiconductor material according to any one of claims 1 to 5, characterized in that: The mass ratio of the main transport material to the photosensitive doping material is 1:(1-10).

7. The organic semiconductor material according to any one of claims 1 to 5, characterized in that: The mass ratio of the donor of the photosensitive doping material to the acceptor of the photosensitive doping material is 1:(1-20).

8. An organic field effect transistor, characterized in that: The semiconductor layer of the organic field effect transistor comprises the organic semiconductor material according to any one of claims 1 to 7.

9. The organic field effect transistor according to claim 8, characterized in that: Further including: substrate; A source electrode and a drain electrode, wherein the source electrode and the drain electrode are arranged at one side of the substrate at intervals; The semiconductor layer is located on a side of the source electrode and the drain electrode away from the substrate, and the orthographic projections of the source electrode and the drain electrode on the substrate are located within the orthographic projection of the semiconductor layer on the substrate.

10. The organic field effect transistor according to claim 9, characterized in that: Further including: A modification layer, wherein the modification layer is located between the source electrode and the semiconductor layer, and / or the modification layer is located between the drain electrode and the semiconductor layer, and the modification layer includes at least one of N-(2-hydroxyethyl)piperazine, N,N'-bis(2-hydroxyethyl)piperazine, and polyethyleneimine.

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