A method for preparing an N-type polymer field-effect transistor based on a bismuth contact electrode

Abstract

The present invention relates to the technical field of microelectronic materials and devices, and relates to a method for preparing an N-type polymer field-effect transistor based on a bismuth contact electrode; the N-type polymer field-effect transistor has a top-gate bottom-contact structure; first, a bismuth metal film is prepared on a substrate as source and drain electrodes by vacuum evaporation through a mask plate, then an organic semiconductor is spin-coated on the surface as an active layer, and after annealing, an insulator is spin-coated on the surface as a dielectric layer, and finally, an aluminum metal film is evaporated on the dielectric layer through a mask plate as a gate electrode; compared with traditional gold contact electrodes, the contact electrode prepared by this method has significantly improved N-type electrical contact performance, significantly enhanced device performance, and significantly reduced preparation cost.

Description

Technical Field

[0001] The present invention relates to the technical field of microelectronic materials and devices, and in particular to a method for preparing an N-type polymer field effect transistor based on a bismuth contact electrode. Background Art

[0002] Since the invention of the first transistor at Bell Labs in 1947, inorganic semiconductors such as silicon, germanium, and gallium arsenide have been widely used in various integrated circuit components, driving the development of the information industry. However, as Moore's Law continues to approach its physical limits, the traditional integrated circuit industry has faced unprecedented challenges. At the same time, organic electronics has garnered widespread attention due to its inherent advantages such as large area, flexibility, environmental friendliness, and low cost. As one of its key applications, the organic field-effect transistor (OFET) has also experienced rapid development.

[0003] In recent years, OFET has made great progress in structural design and manufacturing process, and its carrier mobility is even comparable to that of amorphous silicon. Carrier injection and transport are two key factors affecting the performance of OFET devices; among them, reducing the device contact resistance ( R c ), which is of great significance to improving the performance of OFETs.

[0004] In fact, as one of the key factors limiting the performance of organic electronic devices, contact resistance ( R c ) can be divided into the interface resistance of the metal and organic semiconductor contact R int and the resistance from the contact to the channel inside the organic semiconductor R bulk It consists of two parts, R int It mainly comes from the energy difference between the Fermi level of the metal electrode and the transport energy level of the organic semiconductor, namely the Schottky barrier; R bulk Affected by the defect transport near the contact surface. In comparison, the former is the dominant factor in the contact resistance of OFET. Therefore, the barrier can be reduced by selecting electrode materials that match the energy level of organic semiconductors to form ohmic contacts to effectively reduce the contact resistance. R c , improving device performance.

[0005] In the development of OFETs, gold (Au) has been a popular choice as the contact electrode material for p-type organic devices due to its high conductivity and work function, excellent chemical stability, and Fermi level close to the highest occupied molecular orbital (HOMO) of p-type organic semiconductors. Simultaneously, a series of physical and chemical methods to reduce the injection barrier between p-type semiconductors and Au are being continuously refined. As a lower-cost alternative to Au, copper (Cu) has also demonstrated superior device performance. In summary, these existing studies have primarily focused on p-type organic semiconductors, while the selection of electrode materials for improving n-type electrical contacts has been a challenge. To reduce the Schottky barrier for electron injection, n-type organic devices require metals with low work functions as contact electrodes. However, low-work-function metals are highly chemically active and readily react with water and oxygen in air, resulting in poor device electrical properties and stability, limiting their development. Therefore, selecting a suitable metal material that provides good electrical contact with n-type organic semiconductors to fabricate high-performance n-type OFETs is crucial.

[0006] Bismuth (Bi) has properties similar to those of arsenic and antimony. Freshly produced, it is a silvery-white, brittle metal, but its surface turns pink after oxidation. Bismuth is a unique metal, naturally diamagnetic and possessing one of the lowest thermal conductivity of any metal. Bismuth has long been considered one of the most stable elements with the highest atomic number. Because of its extremely long half-life, its negligible radioactivity has no biological impact (even lower than the human body's own radioactivity levels), and its discovery was only speculated based on physical models.

[0007] Bismuth metal also exhibits excellent electrical contact performance in new semiconductor devices, especially in the field of two-dimensional devices. Experiments have shown that the Bi contact of single-molecule MoS2 produces R c The measured contact resistance is comparable to that of conventional silicon-based devices, approaching the quantum limit. The study also indicates that the interstitial state saturation mechanism at the Bi-MoS2 interface is applicable to various two-dimensional semiconductors, significantly improving the performance and stability of two-dimensional semiconductor devices. This unconventional, excellent N-type electrical contact performance is also of great significance for the fabrication of high-performance N-type OFETs. However, the unique performance advantages of bismuth metal have yet to be explored and demonstrated. Summary of the Invention

[0008] The present invention aims to address the shortcomings of the prior art by providing a method for preparing an N-type polymer field-effect transistor (PFET) with a bismuth contact electrode. This method is applicable to PFETs with a top-gate, bottom-contact structure, where the transistor comprises, from top to bottom, a gate, a dielectric layer, a semiconductor layer, a source and drain electrodes, and a glass substrate. This method utilizes semi-metallic bismuth instead of gold as the source and drain electrode material, significantly reducing the fabrication cost of the PFET, optimizing the contact between the polymer semiconductor N2200 and the bismuth electrode, and significantly improving the electrical performance of the PFET.

[0009] In order to achieve the above object, the present invention is implemented by the following technical solution: a method for preparing an N-type polymer field effect transistor based on a bismuth contact electrode, the method being as follows:

[0010] Step S1: Preparation of solution:

[0011] Step S1-1: Preparation of semiconductor solution;

[0012] Step S1-2: preparing a dielectric layer solution;

[0013] Step S2: Select a substrate and clean it;

[0014] Step S3: Preparation of source and drain electrodes:

[0015] Using vacuum evaporation, bismuth particles are first placed in a metal tungsten boat, and then the cleaned source and drain electrode masks and substrate are adsorbed on magnetic stickers and sent into the cavity of the evaporator. The vacuum degree of the evaporator cavity is pumped to 5*10 using a mechanical pump and a molecular pump. -4 Pa; then slowly increase the power applied to both ends of the metal tungsten boat to increase the boat temperature to melt the bismuth particles. After the bismuth particles are melted, control the bismuth gas flow rate to maintain at 0.2 Å / s;

[0016] Step S4: Preparation of organic semiconductor layer:

[0017] The substrate surface in step S3 was cleaned and transferred to a nitrogen glove box. The semiconductor solution in step S1 was dropped onto the substrate surface using a pipette. The substrate was pre-spin coated at 500 rpm / s for 10 s and then spin coated at 2000 rpm / s for 60 s. After spin coating, the substrate was pre-annealed at 80°C for 5 min and then annealed at 200°C for 20 min. After annealing, the substrate was removed from the heating stage and cooled at room temperature for 30 min.

[0018] Step S5: Preparation of polymer dielectric layer:

[0019] After the sample in step S4 has finished cooling, it is placed on a spin coater. The dielectric layer solution in step S1 is dropped onto the sample surface using a pipette. The sample is pre-spin-coated at 500 rpm / s for 5 seconds and then spin-coated at 2000 rpm / s for 60 seconds. After spin coating, the sample is annealed at 80°C overnight. After annealing, the sample is removed from the heating stage and cooled at room temperature for 30 minutes.

[0020] Step S6: Preparation of gate

[0021] Using high-temperature evaporation, aluminum metal particles are first placed in a metal tungsten boat. Then, the cleaned gate electrode mask and the sample in step S5 are adsorbed on a magnetic sticker and sent into the chamber of the evaporator. The vacuum degree of the evaporator chamber is pumped to 5*10 using a mechanical pump and a molecular pump. -4 Pa; then slowly increase the power applied to both ends of the metal tungsten boat to increase the temperature of the boat to melt the metal aluminum particles. After the aluminum particles are melted, control the aluminum metal gas flow rate to maintain at 0.2 Å / s.

[0022] Preferably, the specific steps of preparing the semiconductor solution in step S1-1 are as follows: preparing the organic semiconductor material and the organic solvent at a mass volume ratio of 7 mg / mL to obtain a semiconductor solution; placing the prepared semiconductor solution on a heating table at 80°C and heating it for more than 48 hours until it is completely dissolved.

[0023] Preferably, the organic semiconductor material is polymer P(NDI2OD-T2), namely N2200; and the organic solvent is o-dichlorobenzene solution, namely DCB solution.

[0024] Preferably, the specific steps of preparing the dielectric layer solution in step S1-2 are as follows: the dielectric layer material and the organic solvent are prepared at a mass volume ratio of 80 mg / mL to obtain a dielectric layer solution; the prepared dielectric layer solution is placed on a heating table at 80°C and heated for more than 24 hours until it is completely dissolved.

[0025] Preferably, the dielectric layer material is polymethyl methacrylate (PMMA); and the organic solvent is n-butanol solution (N-BA solution).

[0026] Preferably, the specific steps of selecting and cleaning the substrate in step S2 are as follows: a high borosilicate glass sheet with a side length of 15 mm and a thickness of 4 mm is selected as the substrate; the high borosilicate glass sheet substrate is placed in alcohol, deionized water, and alcohol in turn, and cleaned with an ultrasonic cleaner for 20 minutes respectively, then blown dry with a nitrogen gun until there are no water droplets on the surface, and then placed on a 100°C heating table and heated for 15 minutes to completely dry the water vapor on the surface, and finally the substrate is placed in a cleaning instrument and cleaned for 30 minutes.

[0027] Preferably, the thickness of the source and drain electrodes in step S3 is 50 nm.

[0028] The present invention uses bismuth metal electrodes instead of commonly used precious metal gold to produce high molecular polymer transistors, optimizes the electrical contact performance of N-type polymer transistors, thereby reducing costs and improving device performance.

[0029] The present invention has the following beneficial effects: the polymer field-effect transistor prepared by the present invention has better contact effect between its metal electrode and the semiconductor active layer; the carrier mobility and output current of the device are significantly improved, and the threshold voltage of the device is also reduced; it can be seen that in the top-gate bottom-contact polymer transistor of the present invention, compared with traditional devices using gold as electrodes, the electrical performance is improved while the preparation cost is greatly reduced.

[0030] The organic semiconductor material in the present invention is a polymer P(NDI2OD-T2), namely N2200, CAS 2173524-17-7, with the molecular formula shown below:

[0031] . BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of the cross-sectional structure of an N-type polymer field-effect transistor prepared in the embodiment;

[0033] Figure 2 A comparison diagram of transfer characteristic curves of the N-type polymer field effect transistors prepared in the comparative example and the example working in the saturation region;

[0034] Figure 3 A comparison diagram of transfer characteristic curves of the N-type polymer field effect transistors prepared in the comparative example and the example working in the linear region;

[0035] Figure 4 The N-type polymer field effect transistor prepared in the comparative example and the embodiment works at V g =Comparison of output characteristic curves when 60 V is applied;

[0036] Figure 5 This is a comparison chart of the contact resistance of the N-type polymer field effect transistor prepared in the comparative example and the embodiment at different gate voltages extracted by the M-TLM method. Implementation Method

[0037] This invention uses a vacuum evaporation electrode deposition process to deposit bismuth metal source and drain electrodes on a glass substrate under self-alignment using a mask. By increasing the power applied to the ends of a tungsten boat, its resistance generates heat, melting the bismuth metal particles on the boat and subsequently vaporizing them. The metal ions form a gas flow that flies upward to the target sample surface, where they condense into a metal film. A mask is then applied to the sample surface to pattern the metal film, forming the electrodes. Unlike traditional gold electrodes, the present invention uses bismuth as an electrode. Its work function is only 4.1 eV, nearly 1 eV lower than gold's 5.1 eV, enabling a better match with the LUMO energy level (-3.0-4.0 eV) of most N-type semiconductors. This reduces the Schottky barrier between the two, improves charge injection efficiency, and enhances device performance. Furthermore, bismuth, a metal with global reserves second only to silver, has a production cost three times lower than traditional gold. Therefore, this invention enables the fabrication of N-type polymer field-effect transistors with superior performance and low cost.

[0038] The present invention will be further described below with reference to the examples, but they are not intended to limit the present invention. Example

[0039] A method for preparing an N-type polymer field-effect transistor based on a bismuth contact electrode, the method being as follows:

[0040] Step S1: Preparation of solution:

[0041] Step S1-1: Preparation of semiconductor solution:

[0042] An organic semiconductor material and an organic solvent are prepared at a mass-to-volume ratio of 7 mg / mL to obtain a semiconductor solution. The prepared semiconductor solution is placed on an 80°C heating table and heated for more than 48 hours until it is completely dissolved. The organic semiconductor material is a polymer P(NDI2OD-T2), namely N2200; and the organic solvent is an o-dichlorobenzene solution, namely DCB solution.

[0043] Step S1-2: Preparation of dielectric layer solution:

[0044] A dielectric layer material and an organic solvent are prepared at a mass-to-volume ratio of 80 mg / mL to obtain a dielectric layer solution; the prepared dielectric layer solution is placed on a heating table at 80°C and heated for more than 24 hours until completely dissolved; wherein the dielectric layer material is polymethyl methacrylate (PMMA); and the organic solvent is an n-butanol solution (N-BA solution);

[0045] Step S2: Select a substrate and clean it;

[0046] A borosilicate glass substrate with a side length of 15 mm and a thickness of 4 mm was selected as the substrate. The borosilicate glass substrate was placed in alcohol, deionized water, and alcohol, respectively, and cleaned in an ultrasonic cleaner for 20 minutes. Then, it was blown dry with a nitrogen gun until there were no water droplets on the surface. The substrate was then heated on a 100°C heating table for 15 minutes to completely dry out the surface moisture. Finally, the substrate was placed in a UVozone cleaner for 30 minutes.

[0047] Step S3: Preparation of source and drain electrodes:

[0048] Using vacuum evaporation, bismuth particles are first placed in a metal tungsten boat, and then the cleaned source and drain electrode masks and substrate are adsorbed on magnetic stickers and sent into the cavity of the evaporator. The vacuum degree of the evaporator cavity is pumped to 5*10 using a mechanical pump and a molecular pump. -4 Pa; then slowly increase the power applied to both ends of the metal tungsten boat to raise the boat temperature and melt the bismuth particles. After the bismuth particles are melted, the bismuth gas flow rate is controlled to maintain at 0.2 Å / s to prepare 50 nm source and drain electrodes;

[0049] Step S4: Preparation of organic semiconductor layer:

[0050] The substrate surface in step S3 was cleaned and transferred to a nitrogen glove box. The semiconductor solution in step S1 was dropped onto the substrate surface using a pipette. The substrate was pre-spin coated at 500 rpm / s for 10 s and then spin coated at 2000 rpm / s for 60 s. After spin coating, the substrate was pre-annealed at 80°C for 5 min and then annealed at 200°C for 20 min. After annealing, the substrate was removed from the heating stage and cooled at room temperature for 30 min.

[0051] Step S5: Preparation of polymer dielectric layer:

[0052] After the sample in step S4 has finished cooling, it is placed on a spin coater. The dielectric layer solution in step S1 is dropped onto the sample surface using a pipette. The sample is pre-spin-coated at 500 rpm / s for 5 seconds and then spin-coated at 2000 rpm / s for 60 seconds. After spin coating, the sample is annealed at 80°C overnight. After annealing, the sample is removed from the heating stage and cooled at room temperature for 30 minutes.

[0053] Step S6: Preparation of gate

[0054] Using high-temperature evaporation, aluminum metal particles are first placed in a metal tungsten boat. Then, the cleaned gate electrode mask and the sample in step S5 are adsorbed on a magnetic sticker and sent into the chamber of the evaporator. The vacuum degree of the evaporator chamber is pumped to 5*10 using a mechanical pump and a molecular pump. -4Pa; then slowly increase the power applied to both ends of the metal tungsten boat to increase the temperature of the boat to melt the metal aluminum particles. After the aluminum particles are melted, control the aluminum metal gas flow rate to maintain at 0.2 Å / s to prepare a 100 nm gate electrode.

[0055] Comparative Example

[0056] Step 1: Solution Preparation

[0057] A1: Solution preparation

[0058] An organic semiconductor material and an organic solvent are prepared at a mass-to-volume ratio of 7 mg / mL; wherein the semiconductor material is a polymer P(NDI2OD-T2), namely N2200; and the organic solvent is an o-dichlorobenzene solution, namely a DCB solution. A dielectric layer material and an organic solvent are prepared at a mass-to-volume ratio of 80 mg / mL; wherein the dielectric layer material is polymethyl methacrylate, namely PMMA; and the organic solvent is an n-butanol solution, namely an N-BA solution.

[0059] A2: Dissolution of solution

[0060] Place the prepared semiconductor solution on a heating table at 80°C and heat for more than 48 hours; place the prepared dielectric layer solution on a heating table at 80°C and heat for more than 24 hours until it is completely dissolved;

[0061] Step 2: Device preparation

[0062] B1: Substrate selection

[0063] A borosilicate glass sheet with a side length of 15 mm and a thickness of 4 mm was selected as the substrate;

[0064] B2: Substrate cleaning

[0065] The substrate was placed in alcohol, deionized water, and alcohol in sequence, and cleaned in an ultrasonic cleaner for 20 minutes each. Then, it was blown dry with a nitrogen gun until there were no water droplets on the surface. The substrate was then placed on a 100°C heating table and heated for 15 minutes to completely dry out the surface moisture. Finally, the substrate was placed in a UVozone cleaner and cleaned for 30 minutes.

[0066] B3: Preparation of source and drain electrodes

[0067] Using vacuum evaporation, gold metal particles are first placed in a metal tungsten boat, and then the cleaned source and drain electrode masks and substrate are adsorbed on magnetic stickers and sent into the cavity of the evaporator. The vacuum degree of the evaporator cavity is pumped to 5*10 using a mechanical pump and a molecular pump. -4Pa; then slowly increase the power applied to both ends of the metal tungsten boat to increase the temperature of the boat to melt the metal gold particles. After the metal particles are melted, control the metal gas flow rate to maintain at 0.2 Å / s to prepare 50 nm source and drain electrodes.

[0068] B4: Preparation of organic semiconductor layer

[0069] The substrate surface was cleaned and transferred to a nitrogen glove box. The semiconductor solution, i.e., N2200 solution, was dropped onto the substrate surface using a pipette. The substrate was pre-spin coated at 500 rpm / s for 10 s and then spin coated at 2000 rpm / s for 60 s. After spin coating, the substrate was pre-annealed at 80°C for 5 minutes and then annealed at 200°C for 20 minutes. After annealing, the substrate was removed from the heating stage and cooled at room temperature for 30 minutes.

[0070] B5: Preparation of polymer dielectric layer

[0071] After the sample has cooled, it is placed on a spin coater. The dielectric layer solution is dropped onto the sample surface using a pipette. The sample is pre-spin-coated at 500 rpm / s for 5 seconds and then spin-coated at 2000 rpm / s for 60 seconds. After spin coating, the sample is annealed at 80°C overnight. After annealing, the sample is removed from the heating stage and cooled at room temperature for 30 minutes.

[0072] B6: Gate Preparation

[0073] Using high-temperature evaporation, aluminum metal particles are first placed in a metal tungsten boat, and then the cleaned gate electrode mask and the above sample are adsorbed on a magnetic sticker and sent into the cavity of the evaporator. The vacuum degree of the evaporator cavity is pumped to 5*10 using a mechanical pump and a molecular pump. -4 Pa; then slowly increase the power applied to both ends of the metal tungsten boat to increase the temperature of the boat to melt the metal aluminum particles. After the metal particles are melted, control the metal gas flow rate to maintain at 0.2 Å / s to prepare a 100 nm gate electrode.

[0074] like Figure 1 As shown, Figure 1 Schematic diagram of the cross-sectional structure of the N-type polymer field-effect transistor prepared in this embodiment;

[0075] Figure 2 , 3 are comparative graphs of the transfer characteristic curves of the N-type polymer field effect transistors prepared in the comparative example and the embodiment working in the saturation region and the linear region. Figure 2 、 3 As shown, the performance of the transistor prepared in the embodiment using bismuth as the source and drain electrodes is significantly improved compared to the performance of the transistor prepared in the comparative example using gold as the source and drain electrodes. Figure 4The N-type polymer field effect transistor prepared in the comparative example and the embodiment works at V g = 60 V when the output characteristic curve comparison diagram. Figure 4 As shown, in V d When the transistor is smaller, the transistor prepared by using bismuth as source and drain electrodes is I d Compared with the transistor prepared by using gold as source and drain electrodes in the comparative example, I d The slope is larger and the value is larger, indicating that its contact resistance R c Compared with the control example, a significant decrease was achieved, and the contact and device performance were significantly improved. Figure 5 The figure is a comparison of the contact resistance of the N-type polymer field effect transistor prepared in the comparative example and the embodiment extracted by the M-TLM method, and its theoretical formula is shown in formula (1). Figure 5 As shown, the contact resistance of the embodiment ( R c W) was significantly reduced compared to the control example.

[0076] (1)

[0077] As shown in Table 1, in order to avoid the introduction of non-intrinsic effects, the comparative examples and the examples are used in V g = 0.5 V in the linear region, the mobility, subthreshold swing, and threshold voltage were extracted, the contact resistance was extracted by M-TLM, and the switching of the two cases was calculated by the working state in the saturation region. For the comparative polymer field effect transistor, its mobility is 0.091 cm 2 / V·s, the subthreshold swing is 3.805 V / dec, and the threshold voltage reaches 1.420 V. V g - V t =5 V, the contact resistance reaches 3.970×10 6 Ω·cm, and its on / off ratio reaches 53161.962; while for the polymer field effect transistor of the embodiment of the present invention, its mobility is 0.107 cm 2 / V·s, the subthreshold swing is 3.840 V / dec, and the threshold voltage reaches 0.726 V. V g - V t =5 V, its contact resistance reaches 1.734×10 6Ω·cm, which is more than 50% lower than that of the control, while its on / off ratio reaches 54495.291, which is a certain improvement compared to the control. Therefore, from the above electrical parameter indicators, it can be seen that the electrical contact state of the polymer field-effect transistor prepared by the present invention is significantly improved compared to the traditional polymer field-effect transistor with gold as the source and drain electrodes, while the manufacturing cost is greatly reduced.

[0078] Table 1

[0079] Electrical parameters Bismuth electrode Gold electrode Threshold voltage (V) 0.726 1.420 Subthreshold swing (V / dec) 3.840 3.805 <![CDATA[Mobility (cm 2 / V·s)]]> 0.107 0.091 <![CDATA[Contact resistance (Ω·cm) @ V g - V t = 5 V]]> <![CDATA[1.734×10 6 ]]> <![CDATA[3.970×10 6 ]]> On / Off ratio 54495.291 53161.962

[0080] The primary cause of electrical contact resistance is the Schottky barrier, an energy barrier formed between the metal electrode and the semiconductor. This is due to the energy difference between the metal work function and the semiconductor's electron affinity, as well as the presence of metal-induced gap states (MIGS), which produce a Fermi level pinning effect. When a semiconductor is close to a metal surface, the extended wave function from the metal perturbs the semiconductor's environment, causing rehybridization of the semiconductor's original wave function. Metal-semiconductor contact causes perturbations in the electronic structure, with MIGS being a significant perturbation. MIGS are electronic states formed by metal electrons in the semiconductor's band gap, with energies close to the metal's Fermi level. The MIGS density profile is similar to that of the metal, including contributions from both the valence and conduction bands. Compared to the original density of states before the semiconductor contact, the MIGS density profile is more complex. Consequently, the metal-induced gap states are greatly suppressed, allowing them to be filled and saturated. This phenomenon is known as gap state saturation. The semiconductor in contact with the semimetallic bismuth is in a degenerate state, and a Schottky barrier forms at the interface. This gap-state saturation mechanism has been applied to various two-dimensional semiconductor materials, which helps improve transistor performance and make it more reliable and efficient. In terms of polymer transistors, bismuth has a high band match with polymer LUMO, so it is used to replace traditional gold as the source and drain electrodes of N-type polymer transistors. It can effectively reduce the Schottky barrier caused by the energy level difference between metal and semiconductor, thereby greatly improving the efficiency of electron injection and reducing its contact resistance, thereby achieving improved electrical performance. Experiments show that the electrical contact state of bismuth as an electrode is significantly improved compared to traditional gold electrodes. The device contact resistance directly drops by more than 50%, and the switching ratio is also improved to a certain extent. Both of these are mainly due to the contact state between the electrode and the organic semiconductor. By achieving energy level matching between the two, the charge injection barrier is reduced, thereby improving the performance of the device.

[0081] Therefore, through the preparation method of the present invention, the point contact state of the N-type polymer field-effect transistor can be significantly improved, the relevant performance of the device can be significantly improved, and the problems caused by the contact between the metal electrode and the semiconductor are improved. Moreover, since the cost of bismuth is three times lower than that of gold, this method has a very profound significance for realizing the application of N-type polymer field-effect transistors.

[0082] The above shows and describes the basic principles, main features, and advantages of the present invention. However, the above is only a specific embodiment of the present invention, and the technical features of the present invention are not limited thereto. Any other implementation methods derived by any person skilled in the art without departing from the technical solution of the present invention should be included in the patent scope of the present invention.

Claims

1. A method for preparing an N-type polymer field effect transistor based on a bismuth contact electrode, characterized in that: The method is as follows: Step S1: Preparation of solution: Step S1-1: Preparation of semiconductor solution; Step S1-2: preparing a dielectric layer solution; Step S2: Select a substrate and clean it; Step S3: Preparation of source and drain electrodes: Using vacuum evaporation, bismuth particles are first placed in a metal tungsten boat, and then the cleaned source and drain electrode masks and substrate are adsorbed on magnetic stickers and sent into the cavity of the evaporator. The vacuum degree of the evaporator cavity is pumped to 5*10 using a mechanical pump and a molecular pump. -4 Pa; then slowly increase the power applied to both ends of the metal tungsten boat, and after the bismuth particles melt, control the bismuth gas flow rate to maintain at 0.2 Å / s; Step S4: Preparation of organic semiconductor layer: The substrate surface in step S3 was cleaned and transferred to a nitrogen glove box. The semiconductor solution in step S1 was dropped onto the substrate surface using a pipette. The substrate was pre-spin coated at 500 rpm / s for 10 s and then spin coated at 2000 rpm / s for 60 s. After spin coating, the substrate was pre-annealed at 80°C for 5 min and then annealed at 200°C for 20 min. After annealing, the substrate was removed from the heating stage and cooled at room temperature for 30 min. Step S5: Preparation of polymer dielectric layer: After the sample in step S4 has finished cooling, it is placed on a spin coater. The dielectric layer solution in step S1 is dropped onto the sample surface using a pipette. The sample is pre-spin coated at 500 rpm / s for 5 seconds and then spin coated at 2000 rpm / s for 60 seconds. After spin coating, the sample is annealed at 80°C overnight. After annealing, the sample is removed from the heating stage and cooled at room temperature for 30 minutes. Step S6: Preparation of gate Using high-temperature evaporation, aluminum metal particles are first placed in a metal tungsten boat. Then, the cleaned gate electrode mask and the sample in step S5 are adsorbed on a magnetic sticker and sent into the chamber of the evaporator. The vacuum degree of the evaporator chamber is pumped to 5*10 using a mechanical pump and a molecular pump. -4 Pa; then slowly increase the power applied to both ends of the metal tungsten boat, and after the aluminum metal particles melt, control the aluminum metal gas flow rate to maintain at 0.2 Å / s.

2. The method for preparing an N-type polymer field effect transistor based on a bismuth contact electrode according to claim 1, characterized in that: The specific steps of step S1-1 are as follows: the organic semiconductor material and the organic solvent are prepared at a mass volume ratio of 7 mg / mL to obtain a semiconductor solution; the prepared semiconductor solution is placed on a heating table at 80°C and heated for more than 48 hours until it is completely dissolved.

3. The method for preparing an N-type polymer field effect transistor based on a bismuth contact electrode according to claim 2, characterized in that: The organic semiconductor material is polymer P(NDI2OD-T2), namely N2200; and the organic solvent is o-dichlorobenzene solution.

4. The method for preparing an N-type polymer field effect transistor based on a bismuth contact electrode according to claim 1, characterized in that: The specific steps of preparing the dielectric layer solution in step S1-2 are as follows: the dielectric layer material and the organic solvent are prepared at a mass volume ratio of 80 mg / mL to obtain a dielectric layer solution; the prepared dielectric layer solution is placed on a heating table at 80°C and heated for more than 24 hours until it is completely dissolved.

5. The method for preparing an N-type polymer field effect transistor based on a bismuth contact electrode according to claim 4, characterized in that: The dielectric layer material is polymethyl methacrylate; the organic solvent is n-butanol solution.

6. The method for preparing an N-type polymer field effect transistor based on a bismuth contact electrode according to claim 1, characterized in that: The specific steps of selecting and cleaning the substrate in step S2 are as follows: a borosilicate glass sheet with a side length of 15 mm and a thickness of 4 mm is selected as the substrate; the borosilicate glass sheet substrate is placed in alcohol, deionized water, and alcohol in turn, and cleaned with an ultrasonic cleaner for 20 minutes respectively, then blown dry with a nitrogen gun until there are no water droplets on the surface, and then placed on a 100°C heating table and heated for 15 minutes to completely dry the water vapor on the surface, and finally placed in a cleaning instrument for cleaning for 30 minutes.

7. The method for preparing an N-type polymer field effect transistor based on a bismuth contact electrode according to claim 1, characterized in that: The thickness of the source and drain electrodes in step S3 is 50 nm.

8. The method for preparing an N-type polymer field effect transistor based on a bismuth contact electrode according to claim 1, characterized in that: The thickness of the gate electrode in step S6 is 100 nm.

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