Organic phototransistor and preparation method therefor

Abstract

The present application relates to the technical field of semiconductors, and relates to an organic phototransistor and a preparation method therefor, used for solving the technical problem in the prior art of lacking of a high-performance organic infrared photodetector. The preparation method for the organic phototransistor comprises the following steps: forming a source electrode and a drain electrode on a substrate, wherein a trench region is present between the source electrode and the drain electrode; forming a P-type organic photoelectric semiconductor active layer on the source electrode and the substrate, wherein the P-type organic photoelectric semiconductor active layer covers a first partial region, close to the source electrode, in the trench region and a partial region of the source electrode adjacent to the first partial region; and forming an N-type organic photoelectric semiconductor active layer on the drain electrode, the substrate, and the P-type organic photoelectric semiconductor active layer, wherein the N-type organic photoelectric semiconductor active layer covers a second partial region, close to the drain electrode, in the trench region and a partial region of the drain electrode adjacent to the second partial region, and the first partial region overlaps the second partial region in the trench region.

Description

Organic phototransistor and preparation method thereof Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to an organic phototransistor and a method for preparing the same. Background Art

[0002] In recent years, organic electronic devices such as organic field effect transistors (OFETs), organic photovoltaic devices (OPVs), and organic light-emitting diodes (OLEDs) have developed rapidly, with their performance now comparable to that of corresponding amorphous silicon devices. Photodetectors (PDs) are key components of many optoelectronic devices, converting photons of varying incident energy into adjustable electrical signals. Depending on the wavelength of the photons they absorb, photodetectors can be divided into ultraviolet, visible, and infrared photodetectors. The near-infrared band within the infrared band primarily refers to light with a wavelength greater than 800 nm and less than 2500 nm. It has attracted widespread attention due to its broad application prospects in remote sensing, health monitoring, spectral analysis, and night vision.

[0003] Traditional photodetectors using inorganic silicon-based materials as active layers are much more stable than organic semiconductors. However, adjusting the parameters of traditional silicon semiconductor devices is primarily achieved through complex doping processes or the introduction of microstructures such as superlattices. The absorption range of photoelectric materials is primarily determined by the material's band gap, which cannot be achieved through complex doping processes or the introduction of microstructures such as superlattices. In the infrared region, due to the longer wavelength of absorbed photons, the corresponding material's band gap is smaller. Therefore, the performance of most silicon semiconductor materials as active layers in the field of infrared wavelength detection remains unsatisfactory.

[0004] Organic semiconductors (OSCs) are semiconductor materials primarily composed of compounds containing carbon atoms. Compared to traditional silicon-based semiconductors, organic semiconductors offer irreplaceable advantages, including the ability to easily adjust their optical and electrical properties through molecular structure, inherent flexibility, compatibility with large-scale, low-temperature manufacturing processes (such as roll-to-roll and inkjet printing), and compatibility with biomaterials. In recent years, driven by potential applications in remote control, night vision, imaging, and biomedical monitoring, infrared organic photodetectors sensitive to light wavelengths above 800 nm have rapidly developed.

[0005] However, for existing organic infrared photodetectors, further improving their performance faces the following technical obstacles: First, it is very difficult to design and synthesize infrared light-absorbing organic materials with good photoresponsivity and excellent electrical conductivity. Second, the low dielectric constant of organic materials causes them to produce highly localized, tightly bound Frenkel excitons (electron-hole pairs) under light, resulting in a low dissociation efficiency of photogenerated excitons. Third, the gap between the highest occupied molecular orbital energy level and the lowest unoccupied molecular orbital energy level of the infrared light-absorbing material is small, resulting in a high dark current. Therefore, carrier injection from the electrode occurs in both light and dark environments. These three points have become bottlenecks in improving the performance of organic infrared photodetectors.

[0006] How to design a next-generation high-sensitivity, high-performance organic infrared photodetector with organic semiconductors as the photoelectric sensing layer is a technical problem that needs to be solved urgently.

[0007] Summary of the Invention

[0008] In view of the above analysis, the embodiments of the present application aim to provide an organic phototransistor and a method for preparing the same, so as to solve the technical problem of the lack of high-performance organic infrared photodetectors in the prior art.

[0009] In one aspect, an embodiment of the present application provides a method for preparing an organic phototransistor, comprising the following steps:

[0010] forming a source electrode and a drain electrode on a substrate, wherein a channel region exists between the source electrode and the drain electrode;

[0011] forming a P-type organic photoelectric semiconductor active layer on the source electrode and the substrate, wherein the P-type organic photoelectric semiconductor active layer covers a first partial region in the channel region close to the source electrode and a partial region of the source electrode adjacent to the first partial region;

[0012] An N-type organic photoelectric semiconductor active layer is formed on the drain electrode, the substrate, and the P-type organic photoelectric semiconductor active layer, wherein the N-type organic photoelectric semiconductor active layer covers a second partial region in the channel region close to the drain electrode and a partial region of the drain electrode adjacent to the second partial region;

[0013] The first partial region and the second partial region overlap in the trench region.

[0014] According to a further improvement of the above method, before forming the P-type organic photoelectric semiconductor active layer and the N-type organic photoelectric semiconductor active layer, the method further includes:

[0015] The source electrode and the drain electrode are immersed in a pentafluorothiophenol solution.

[0016] Based on a further improvement of the above method, forming a P-type organic photoelectric semiconductor active layer on the source electrode and the substrate includes:

[0017] Depositing photoresist on the channel region, the source electrode, and the drain electrode;

[0018] Etching the photoresist by photolithography to pattern a first region of the P-type organic photoelectric semiconductor active layer, wherein the first region includes a first partial region in the channel region close to the source electrode and a partial region of the source electrode adjacent to the first partial region;

[0019] depositing a P-type organic photoelectric semiconductor active layer material on the first region; and

[0020] The etched photoresist is removed using an etching solution.

[0021] Based on a further improvement of the above method, forming an N-type organic photoelectric semiconductor active layer on the drain electrode, the substrate and the P-type organic photoelectric semiconductor active layer includes:

[0022] Depositing photoresist on the P-type organic photoelectric semiconductor active layer, the channel region, the source electrode, and the drain electrode;

[0023] Etching the photoresist by photolithography to pattern and form a second region of the N-type organic optoelectronic semiconductor active layer, wherein the second region includes a second partial region in the channel region close to the drain electrode and a partial region of the drain electrode adjacent to the second partial region, and the first partial region and the second partial region overlap in the channel region;

[0024] depositing an N-type organic photoelectric semiconductor active layer material on the second region; and

[0025] The etched photoresist is removed using an etching solution.

[0026] Based on a further improvement of the above method, the P-type organic photoelectric semiconductor active layer material is an organic P-type organic semiconductor with near-infrared response.

[0027] Based on a further improvement of the above method, the N-type organic photoelectric semiconductor active layer material is an organic N-type polymer or a small molecule photoelectric semiconductor material.

[0028] Based on the further improvement of the above method, the organic P-type semiconductor with near-infrared response is TBOPV-BT, and its molecular formula is:

[0029] The molecular formula of R is:

[0030] Alternatively, another typical organic P-type semiconductor with near-infrared response is PBDPT2F2T, whose molecular formula is:

[0031] Based on the further improvement of the above method, the organic N-type polymer or small molecule optoelectronic semiconductor material is any one of the following:

[0032] L8-BO, BTP-eC9.

[0033] On the other hand, an embodiment of the present application provides an organic phototransistor, comprising:

[0034] substrate;

[0035] a source electrode and a drain electrode, wherein the source electrode and the drain electrode are located on the substrate, and a channel region exists between the source electrode and the drain electrode;

[0036] a P-type organic photoelectric semiconductor active layer, the P-type organic photoelectric semiconductor active layer being located on the source electrode and the substrate, and covering a first partial region in the channel region close to the source electrode and a partial region of the source electrode adjacent to the first partial region;

[0037] an N-type organic photoelectric semiconductor active layer, the N-type organic photoelectric semiconductor active layer being located on the drain electrode, the substrate, and the P-type organic photoelectric semiconductor active layer, and covering a second partial region in the channel region close to the drain electrode and a partial region of the drain electrode adjacent to the second partial region, and the first partial region and the second partial region overlapping in the channel region.

[0038] Compared with the prior art, this application can achieve at least one of the following beneficial effects:

[0039] 1. The organic phototransistor provided in this application uses both P-type and N-type organic photoelectric semiconductor materials as the active layer. The transfer curve of this organic heterostructure phototransistor exhibits bipolar transmission characteristics. Under near-infrared wavelength light irradiation, the device's bipolar transfer curve shifts to the right, thereby achieving positive and negative photoelectric responses under different gate voltages. That is, under different gate voltages, light-induced source-drain current increases, which is a positive response; conversely, light-induced source-drain current decreases, which is a negative response. Furthermore, the device can achieve positive and negative photoelectric responses to a variety of near-infrared wavelengths, and different wavelengths of near-infrared light can be selected as needed.

[0040] 2. Compared with other materials such as graphene and two-dimensional materials (such as molybdenum disulfide, tungsten diselenide, etc.), the organic materials used in the organic phototransistors provided by this application have easily adjustable band gaps, especially narrow band gap (such as <1.6eV) conjugated polymers, which can be used for near-infrared optoelectronic applications such as fluorescence imaging, medical monitoring, and optical communications. In addition, the organic materials used in the organic phototransistors provided by this application also have the advantages of intrinsic flexibility, rich material system selection, good biocompatibility, low preparation temperature, large-area fabrication, and formation on heterogeneous substrates, and have great potential in the field of near-infrared sensing and computing device manufacturing.

[0041] 3. By designing a heterostructure composed of a P-type conjugated polymer TBOPV-BT and an N-type small molecule, this application innovatively proposes a lithography-compatible organic heterostructure fabrication process, achieving a channel length of only 5 microns, a feat previously unattainable for large-scale (hundreds of millimeters) organic heterojunction structures based on small molecules. This lithography-compatible fabrication process minimizes device size and increases monolithic integrated device density (maximum approximately 520 devices per square centimeter).

[0042] 4. The source-drain metal modification layer material was selected to modify the source-drain metal, adjust the Schottky barrier between the source-drain metal and the semiconductor material, reduce the contact resistance between the source-drain electrode and the active layer of the organic heterostructure phototransistor, and improve the performance of the organic heterostructure phototransistor.

[0043] In this application, the above-mentioned technical solutions can be combined with each other to achieve more preferred combination solutions. Other features and advantages of this application will be described in the subsequent description, and some advantages will become apparent from the description or be understood by practicing this application. The objectives and other advantages of this application can be achieved and obtained through the contents particularly pointed out in the description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The accompanying drawings are only used for the purpose of illustrating specific embodiments and are not to be considered as limiting the present application. Throughout the drawings, the same reference symbols denote the same components.

[0045] FIG1 is a schematic flow chart of a method for preparing an organic phototransistor according to an embodiment of the present application.

[0046] FIG. 2 is a schematic diagram showing a conceptual structure of a source electrode and a drain electrode formed according to step 101 .

[0047] FIG. 3 shows a conceptual structural diagram of a P-type organic photoelectric semiconductor active layer formed according to step 102 .

[0048] FIG. 4 shows a conceptual structural diagram of an N-type organic photoelectric semiconductor active layer formed according to step 103 .

[0049] FIG5 is a schematic flow chart of a method for preparing an organic phototransistor according to another embodiment of the present application.

[0050] FIG6 is a schematic diagram of the transfer curve of the organic heterostructure phototransistor of the present application.

[0051] FIG7 is a schematic diagram of the transfer curves of the negative gate voltage portion (having a positive photoelectric response) of the organic heterostructure phototransistor of the present application before and after illumination.

[0052] FIG8 is a schematic diagram of the transfer curves of the positive gate voltage portion (having a negative photoelectric response) of the organic heterostructure phototransistor of the present application before and after illumination.

[0053] FIG9 is a schematic diagram showing the source-drain current variation when a positive photoelectric response is generated under 1050 nm wavelength light of different light intensities at a gate voltage of -50 V, and a negative photoelectric response is generated under 1050 nm wavelength light of different light intensities at a gate voltage of 50 V.

[0054] FIG10 is a schematic diagram showing the source-drain current changes of positive and negative photoelectric responses generated under different gate voltage conditions under illumination of 1050 nm and 1200 nm wavelengths, respectively. DETAILED DESCRIPTION

[0055] The preferred embodiments of the present application are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present application and are used together with the embodiments of the present application to illustrate the principles of the present application, and are not used to limit the scope of the present application.

[0056] FIG1 is a schematic flow chart of a method for preparing an organic phototransistor according to an embodiment of the present application.

[0057] An embodiment of the present application is described below with reference to FIG1 .

[0058] As shown in FIG1 , the method for preparing the organic phototransistor includes the following steps:

[0059] Step 101: forming a source electrode and a drain electrode on a substrate.

[0060] FIG. 2 is a schematic diagram showing a conceptual structure of a source electrode and a drain electrode formed according to step 101 .

[0061] The following is an explanation with reference to FIG2 .

[0062] As shown in FIG2 , in step 101, the substrate 1 may include, but is not limited to, a rigid or flexible substrate such as SiO2, glass, or polyimide (PI). Before forming the source and drain electrodes 2, the source and drain electrode regions to be formed may be patterned by photolithography. For example, a layer of photoresist may be first deposited on the substrate 1, and then the photoresist may be photolithographically processed using a mask to obtain regions where the source and drain electrodes are to be formed. Subsequently, a layer of source and drain electrode metal material is deposited on the regions where the source and drain electrodes are to be formed. The source and drain electrode metal material may be deposited by any of electron beam evaporation, thermal evaporation, magnetron sputtering, or the like. The source and drain electrode metal material may include, but is not limited to, one or a combination of gold (Au), titanium (Ti), or silver (Ag). After the source and drain electrode metal material is deposited, the excess source and drain electrode metal material and photoresist may be removed using a corrosive solution such as acetone or a degumming solution to complete the patterning of the source and drain electrodes.

[0063] Step 102: forming a P-type organic photoelectric semiconductor active layer on the source electrode and the substrate.

[0064] FIG. 3 shows a conceptual structural diagram of a P-type organic photoelectric semiconductor active layer formed according to step 102 .

[0065] The following is an explanation with reference to FIG3 .

[0066] In this embodiment, a photoresist may be first deposited on the channel region, the source electrode, and the drain electrode, and then the photoresist may be etched using a photolithography technique to pattern and form the first region of the P-type organic photoelectric semiconductor active layer.

[0067] As shown in Figure 3, before forming the P-type organic optoelectronic semiconductor active layer 3, the region where the P-type organic optoelectronic semiconductor active layer is to be formed can be patterned using photolithography. For example, a layer of photoresist can be deposited on the structure shown in Figure 2, and then the photoresist can be photolithographically patterned using a mask to obtain the region where the P-type organic optoelectronic semiconductor active layer is to be formed. The region where the P-type organic optoelectronic semiconductor active layer is to be formed is the first region in this embodiment. As shown in Figure 3, the first region includes a first portion of the channel region near the source electrode and a portion of the source electrode adjacent to the first portion.

[0068] Afterwards, a P-type organic optoelectronic semiconductor active layer material can be deposited on the first region. Here, a layer of P-type organic optoelectronic semiconductor active layer material can be deposited on the region where the P-type organic optoelectronic semiconductor active layer is to be formed. The P-type optoelectronic semiconductor active layer material can include any of organic P-type semiconductor materials with near-infrared response, such as TBOPV-BT and PBDPT2F2T. The molecular formula of TBOPV-BT is:

[0069] The molecular formula of R is:

[0070] The molecular formula of PBDPT2F2T is:

[0071] The P-type organic optoelectronic semiconductor active layer material can be deposited by any of thermal evaporation, inkjet printing, Czochralski coating, spin coating, or drop coating. When using thermal evaporation, inkjet printing, Czochralski coating, spin coating, or drop coating, the solvent of the P-type organic optoelectronic semiconductor solution can be an organic solvent such as chloroform or chlorobenzene, with a concentration between 0.1 mg / mL and 10 mg / mL. The spin coating speed can be 1000-3000 rpm, and the Czochralski coating speed can be 50-1000 μm / s.

[0072] Finally, the etched photoresist can be removed using an etchant. After depositing the P-type organic optoelectronic semiconductor active layer material, an annealing process can be performed at a temperature of 100°C to 300°C for 30 to 120 minutes. After annealing, excess photoresist and the P-type organic optoelectronic semiconductor active layer material can be removed using an etchant such as acetone or a degumming solution, resulting in the structure shown in Figure 3.

[0073] Step 103: forming an N-type organic photoelectric semiconductor active layer on the drain electrode, the substrate and the P-type organic photoelectric semiconductor active layer.

[0074] FIG. 4 shows a conceptual structural diagram of an N-type organic photoelectric semiconductor active layer formed according to step 103 .

[0075] The following is an explanation with reference to FIG4 .

[0076] In this embodiment, a photoresist may be first deposited on the P-type organic optoelectronic semiconductor active layer, the channel region, the source electrode, and the drain electrode, and then the photoresist is etched using a photolithography technique to pattern the second region of the N-type organic optoelectronic semiconductor active layer.

[0077] As shown in FIG4 , before forming the N-type organic optoelectronic semiconductor active layer 4, photolithography can be used to pattern the region of the N-type organic optoelectronic semiconductor active layer to be formed. The region where the N-type organic optoelectronic semiconductor active layer is to be formed is the second region in this embodiment. As shown in FIG4 , the second region includes a second partial region in the channel region near the drain electrode and a partial region of the drain electrode adjacent to the second partial region, with the first partial region and the second partial region overlapping in the channel region.

[0078] For example, a layer of photoresist may be first deposited on the structure of FIG3 , and then the photoresist may be photolithographically processed using a mask to obtain a region where the N-type organic photoelectric semiconductor active layer needs to be fabricated.

[0079] Subsequently, an N-type organic optoelectronic semiconductor active layer material can be deposited on the second region. Here, a layer of N-type organic optoelectronic semiconductor active layer material can be deposited on the region where the N-type organic optoelectronic semiconductor active layer is to be formed. The N-type organic optoelectronic semiconductor active layer material can include any organic N-type polymer, such as L8-BO and BTP-eC9, or a small molecule optoelectronic semiconductor material.

[0080] The N-type organic optoelectronic semiconductor active layer material can be deposited by any of thermal evaporation, inkjet printing, Czochralski coating, spin coating, and drop coating. When using thermal evaporation, inkjet printing, Czochralski coating, spin coating, or drop coating, the solvent of the N-type organic optoelectronic semiconductor solution can be dichloromethane, and the concentration can be between 0.1 mg / mL and 10 mg / mL. The spin coating speed can be 1000-3000 rpm, and the Czochralski coating speed can be 50-1000 μm / s.

[0081] Finally, the etched photoresist can be removed using a corrosive solution. After the N-type organic optoelectronic semiconductor active layer material is deposited, it can undergo an annealing process at a temperature of 100°C-300°C for 0.5h-2h. After the annealing is completed, the excess photoresist and the N-type organic optoelectronic semiconductor active layer material can be removed using a corrosive solution such as acetone or a degumming solution, thereby obtaining the structure shown in FIG4 . As shown in FIG4 , the N-type organic optoelectronic semiconductor active layer and the P-type organic optoelectronic semiconductor active layer overlap in the channel region. It should be noted that this overlapping structure of the N-type organic optoelectronic semiconductor active layer and the P-type organic optoelectronic semiconductor can ensure sufficient lateral contact between the N-type active layer and the P-type active layer, thereby improving the performance of the transistor.

[0082] FIG5 is a schematic flow chart of a method for preparing an organic phototransistor according to another embodiment of the present application.

[0083] Another embodiment of the present application is described below with reference to FIG5 .

[0084] As shown in FIG5 , the method for preparing the organic phototransistor includes the following steps:

[0085] Step 501: forming a source electrode and a drain electrode on a substrate.

[0086] Step 501 is similar to step 101 and will not be described again here.

[0087] Step 502: soaking the source electrode and the drain electrode in a pentafluorothiophenol solution.

[0088] In step 502, the source and drain electrodes may be modified to reduce the contact resistance between the source and drain electrodes and the subsequent active layer. Prior to modification, oxygen plasma treatment may be performed to achieve a surface cleaning effect. The material of the metal modification layer solution may be a 2,3,4,5,6-pentafluorothiophenol (PFBT) solution, the solvent may be anhydrous ethanol, the concentration of the PFBT solution may be selected to be 0.5 μL / mL-5 μL / mL, and the immersion time may be 5 to 6 hours.

[0089] Step 503: forming a P-type organic photoelectric semiconductor active layer on one side of the channel region between the source electrode and the drain electrode.

[0090] Step 503 is similar to step 102 and will not be described again here.

[0091] Step 504: forming an N-type organic photoelectric semiconductor active layer on the other side of the channel region between the source electrode and the drain electrode.

[0092] Step 504 is similar to step 103 and will not be described again here.

[0093] The performance of the organic heterostructure phototransistor of the present application will be described below with reference to FIG. 6 to FIG. 10 .

[0094] It should be noted that the heterostructure here means that the P-type active layer and the N-type active layer of the organic phototransistor in this application are formed based on different organic materials.

[0095] FIG6 is a schematic diagram of the transfer curve of the organic heterostructure phototransistor of the present application. As shown in FIG6, the horizontal axis V G Represents the gate voltage, the vertical axis I ds It represents the current between the source electrode and the drain electrode. From FIG6 , it can be seen that the organic heterostructure phototransistor proposed in this application has a bipolar transfer characteristic.

[0096] FIG7 is a schematic diagram of the transfer curves of the negative gate voltage portion (having a positive photoelectric response) of the organic heterostructure phototransistor of the present application before and after illumination.

[0097] As shown in FIG7 , after the organic heterostructure phototransistor of the present invention is irradiated with near-infrared light, the transfer curve corresponding to the negative gate voltage portion thereof changes. That is, when the same negative gate voltage is applied, the I ds Therefore, the organic heterostructure phototransistor proposed in this application produces a positive photoresponse under near-infrared light.

[0098] FIG8 is a schematic diagram of the transfer curves of the positive gate voltage portion (having a negative photoelectric response) of the organic heterostructure phototransistor of the present application before and after illumination.

[0099] As shown in FIG8 , after the organic heterostructure phototransistor of the present application is irradiated with near-infrared light, the transfer curve corresponding to the positive gate voltage portion thereof changes. That is, when the same positive gate voltage is applied, the I ds Therefore, the organic heterostructure phototransistor proposed in this application produces a negative photoelectric response under near-infrared light.

[0100] FIG9 is a schematic diagram showing the source-drain current variation when a positive photoelectric response is generated under 1050 nm wavelength light of different light intensities at a gate voltage of -50 V, and a negative photoelectric response is generated under 1050 nm wavelength light of different light intensities at a gate voltage of 50 V.

[0101] As shown in Figure 9, different grayscale values ​​represent different light intensities. The larger the grayscale value, the stronger the light intensity. The grayscale value is zero, and the light intensity is zero. The light intensity is represented by the letter P. The three longitudinal strip areas represent the irradiation of the organic heterostructure phototransistor of the present application with three different light intensities. The wavelength of the irradiating light is 1050nm. As can be seen from Figure 9, the organic heterostructure phototransistor proposed in this application can produce a positive photoelectric response under 1050nm wavelength light of different light intensities when the gate voltage is -50V, and a negative photoelectric response under 1050nm wavelength light of different light intensities when the gate voltage is 50V. The gate voltages of -50V and 50V in the figure are both example values. Under other similar gate voltage conditions, the organic heterostructure phototransistor proposed in this application also agrees to show the phenomenon of generating positive and negative photoelectric response currents.

[0102] FIG10 is a schematic diagram showing the source-drain current changes of positive and negative photoelectric responses generated under different gate voltage conditions under illumination of 1050 nm and 1200 nm wavelengths, respectively.

[0103] As shown in FIG10 , the four longitudinal strip regions I, II, III, and IV represent four test conditions, respectively, and their corresponding relationships are as follows: (I) wavelength λ = 1050 nm: V G =-30V,P=84.44μWmm -2 , wavelength λ = 1200 nm: P = 39.33 μW mm -2 ; (II) wavelength λ = 1050nm: V G =-30V,P=57.78μW mm -2 , wavelength λ = 1200 nm: P = 27.00 μW mm -2 (III) wavelength λ = 1050 nm: V G =30V,P=57.78μW mm -2, wavelength λ = 1200nm: P = 27.00μWmm -2； (IV) Wavelength λ = 1050 nm: V G =30V,P=84.44μW mm -2 , wavelength λ = 1200 nm: P = 39.33 μW mm -2 .

[0104] The source-drain current I in Figure 10 ds The changes in indicate that the organic heterostructure phototransistor proposed in this application can generate positive and negative photoelectric responses under light with a wavelength of 1050 nm and 1200 nm, respectively.

[0105] The present application also proposes an organic phototransistor, comprising:

[0106] substrate;

[0107] a source electrode and a drain electrode, wherein the source electrode and the drain electrode are located on the substrate, and a channel region exists between the source electrode and the drain electrode;

[0108] a P-type organic photoelectric semiconductor active layer, the P-type organic photoelectric semiconductor active layer being located on the source electrode and the substrate, and covering a first partial region in the channel region close to the source electrode and a partial region of the source electrode adjacent to the first partial region;

[0109] an N-type organic photoelectric semiconductor active layer, the N-type organic photoelectric semiconductor active layer being located on the drain electrode, the substrate, and the P-type organic photoelectric semiconductor active layer, and covering a second partial region in the channel region close to the drain electrode and a partial region of the drain electrode adjacent to the second partial region, and the first partial region and the second partial region overlapping in the channel region.

[0110] Figure 4 is a schematic diagram of the structure of an organic phototransistor according to an embodiment of the present application. The organic phototransistor has been described above in conjunction with Figure 4 and will not be repeated here.

[0111] Compared with the prior art, the organic phototransistor and the preparation method thereof provided in the embodiments of the present application can achieve at least one of the following beneficial effects:

[0112] 1. The organic phototransistor provided in this application uses both P-type and N-type organic photoelectric semiconductor materials as the active layer. The transfer curve of this organic heterostructure phototransistor exhibits bipolar transmission characteristics. Under near-infrared wavelength light irradiation, the device's bipolar transfer curve shifts to the right, thereby achieving positive and negative photoelectric responses under different gate voltages. That is, under different gate voltages, light-induced source-drain current increases, which is a positive response; conversely, light-induced source-drain current decreases, which is a negative response. Furthermore, the device can achieve positive and negative photoelectric responses to a variety of near-infrared wavelengths, and different wavelengths of near-infrared light can be selected as needed.

[0113] 2. Compared with other materials such as graphene and two-dimensional materials (such as molybdenum disulfide, tungsten diselenide, etc.), the organic materials used in the organic phototransistors provided by this application have easily adjustable band gaps, especially narrow band gap (such as <1.6eV) conjugated polymers, which can be used for near-infrared optoelectronic applications such as fluorescence imaging, medical monitoring, and optical communications. In addition, the organic materials used in the organic phototransistors provided by this application also have the advantages of intrinsic flexibility, rich material system selection, good biocompatibility, low preparation temperature, large-area fabrication, and formation on heterogeneous substrates, and have great potential in the field of near-infrared sensing and computing device manufacturing.

[0114] 3. By designing a heterostructure composed of a P-type conjugated polymer TBOPV-BT and an N-type small molecule, this application innovatively proposes a lithography-compatible organic heterostructure fabrication process, achieving a channel length of only 5 microns, a feat previously unattainable for large-scale (hundreds of millimeters) organic heterojunction structures based on small molecules. This lithography-compatible fabrication process minimizes device size and increases monolithic integrated device density (maximum approximately 520 devices per square centimeter).

[0115] 4. The source-drain metal modification layer material was selected to modify the source-drain metal, adjust the Schottky barrier between the source-drain metal and the semiconductor material, reduce the contact resistance between the source-drain electrode and the active layer of the organic heterostructure phototransistor, and improve the performance of the organic heterostructure phototransistor.

[0116] The above is only a preferred specific implementation method of the present application, but the scope of protection of the present application is not limited thereto. Any changes or replacements that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed in this application should be covered by the scope of protection of the present application.

Claims

1. A method for preparing an organic phototransistor, characterized in that: The steps include: forming a source electrode and a drain electrode on a substrate, wherein a channel region exists between the source electrode and the drain electrode; forming a P-type organic photoelectric semiconductor active layer on the source electrode and the substrate, wherein the P-type organic photoelectric semiconductor active layer covers a first partial region in the channel region close to the source electrode and a partial region of the source electrode adjacent to the first partial region; An N-type organic photoelectric semiconductor active layer is formed on the drain electrode, the substrate, and the P-type organic photoelectric semiconductor active layer, wherein the N-type organic photoelectric semiconductor active layer covers a second partial region in the channel region close to the drain electrode and a partial region of the drain electrode adjacent to the second partial region; The first partial region and the second partial region overlap in the trench region.

2. The method for preparing an organic phototransistor according to claim 1, wherein: Before forming the P-type organic photoelectric semiconductor active layer and the N-type organic photoelectric semiconductor active layer, the method further includes: The source electrode and the drain electrode are immersed in a pentafluorothiophenol solution.

3. The method for preparing an organic phototransistor according to claim 1, wherein: Forming a P-type organic photoelectric semiconductor active layer on the source electrode and the substrate includes: Depositing photoresist on the channel region, the source electrode, and the drain electrode; Etching the photoresist by photolithography to pattern a first region of the P-type organic photoelectric semiconductor active layer, wherein the first region includes a first partial region in the channel region close to the source electrode and a partial region of the source electrode adjacent to the first partial region; depositing a P-type organic photoelectric semiconductor active layer material on the first region; and The etched photoresist is removed using an etching solution.

4. The method for preparing an organic phototransistor according to claim 3, wherein: Forming an N-type organic photoelectric semiconductor active layer on the drain electrode, the substrate and the P-type organic photoelectric semiconductor active layer comprises: In the P-type organic photoelectric semiconductor active layer, the channel region, the source electrode, Depositing photoresist on the drain electrode; Etching the photoresist by photolithography to pattern and form a second region of the N-type organic optoelectronic semiconductor active layer, wherein the second region includes a second partial region in the channel region close to the drain electrode and a partial region of the drain electrode adjacent to the second partial region, and the first partial region and the second partial region overlap in the channel region; depositing an N-type organic photoelectric semiconductor active layer material on the second region; and The etched photoresist is removed using an etching solution.

5. The method for preparing an organic phototransistor according to claim 3, wherein: The P-type organic photoelectric semiconductor active layer material is an organic P-type semiconductor with near-infrared response.

6. The method for preparing an organic phototransistor according to claim 4, wherein: The N-type organic photoelectric semiconductor active layer material is an organic N-type polymer or a small molecule photoelectric semiconductor material.

7. The method for preparing an organic phototransistor according to claim 5, wherein: The organic P-type semiconductor with near-infrared response is TBOPV-BT, and its molecular formula is: The molecular formula of R is: Alternatively, another typical organic P-type semiconductor with near-infrared response is PBDPT2F2T, whose molecular formula is:

8. The method for preparing an organic phototransistor according to claim 6, wherein: The organic N-type polymer or small molecule optoelectronic semiconductor material is: L8-BO, BTP-eC9.

9. An organic phototransistor, characterized in that include: substrate; a source electrode and a drain electrode, wherein the source electrode and the drain electrode are located on the substrate, and a channel region exists between the source electrode and the drain electrode; a P-type organic photoelectric semiconductor active layer, the P-type organic photoelectric semiconductor active layer being located on the source electrode and the substrate, and covering a first partial region in the channel region close to the source electrode and a partial region of the source electrode adjacent to the first partial region; an N-type organic photoelectric semiconductor active layer, the N-type organic photoelectric semiconductor active layer being located on the drain electrode, the substrate, and the P-type organic photoelectric semiconductor active layer, and covering a second partial region in the channel region close to the drain electrode and a partial region of the drain electrode adjacent to the second partial region, and the first partial region and the second partial region overlapping in the channel region.

10. The organic phototransistor according to claim 9, characterized in that The material of the P-type organic photoelectric semiconductor active layer is a P-type organic photoelectric semiconductor material with near-infrared response, and the material of the N-type organic photoelectric semiconductor active layer is an organic N-type polymer or a small molecule photoelectric semiconductor material.

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