CN116163022A

CN116163022A - Preparation method of organic single crystal C8-BTBT, organic field effect transistor and integrated circuit

Info

Publication number: CN116163022A
Application number: CN202310178498.XA
Authority: CN
Inventors: 谭源; 任晓斌; 邓巍; 张秀娟
Original assignee: Suzhou University
Current assignee: Suzhou University
Priority date: 2023-02-28
Filing date: 2023-02-28
Publication date: 2023-05-26

Abstract

The invention provides a preparation method of organic monocrystal C8-BTBT. The preparation method comprises the following steps: preparing and obtaining a patterned water drop structure by utilizing a photoetching method, wherein the patterned water drop structure comprises a silicon substrate and an amorphous high-transparency fluorinated polymer formed on the silicon substrate from bottom to top, the surface of the patterned water drop structure is provided with a plurality of water drop-shaped concave parts which are arrayed, and the water drop-shaped concave parts expose the silicon substrate; C8-BTBT is dissolved in a mixed solvent system formed by mixing a good solvent and a poor solvent, so as to obtain a mixed solution of C8-BTBT; the mixed solution is printed into the patterned water droplet structure by using an inkjet printing method to preferentially nucleate at the tip of the water droplet-shaped recess, then grow from the tip, and self-assemble and grow to fill the entire water droplet-shaped recess along a single orientation, to obtain the organic single crystal C8-BTBT. The scheme of the invention can obtain single-oriented high-quality organic single-machine C8-BTBT.

Description

Preparation method of organic single crystal C8-BTBT, organic field effect transistor and integrated circuit

Technical Field

The invention relates to the technical field of preparation of organic semiconductor single crystals, in particular to a preparation method of an organic single crystal C8-BTBT, an organic field effect transistor and an integrated circuit.

Background

Organic semiconductor single crystals (Organic semiconductor single crystal, OSSCs), which have long range order, no grain boundaries, low defect density, and the like, have been applied to many electronic and optoelectronic devices such as organic field-effect transistors (OFETs), organic light emitting transistors, organic light emitting diodes, and photovoltaic cells. Implementing patterned OSSCs is of great importance for integrated fabrication of highly uniform devices and complex integrated circuits.

At present, the common methods for patterning the organic semiconductor crystal mainly comprise a template auxiliary method, an ink-jet printing method and the like, but the conjugated molecules in the organic crystal are combined by only weak Van der Waals force<10kcal mol ^-1 ) The crystallization quality of the organic crystal is affected by weak external disturbance or disturbance. So far, the nucleation and crystallization process of the organic semiconductor is still difficult to effectively control, so that the obtained crystals have large morphology and structure difference and the deposition positions are randomly distributed, and the repeatability and stability of the performance of the organic single crystal device are difficult to ensure. For example, the patterned small organic molecule C8-BTBT is obtained by an inkjet printing method, a template auxiliary method and a substrate wettability difference method, however, due to the instability of random nucleation positions of seed crystals in a self-assembly process of organic crystals, it is often difficult to obtain patterned high-quality organic semiconductor single crystals, so that the quality of formed crystal thin films is uneven, many defects exist, and finally an ideal stable high-performance device cannot be realized.

Disclosure of Invention

It is an object of the present invention to provide a method capable of precisely anchoring nucleation sites of organic crystals.

It is a further object of the present invention to improve the performance and uniformity of organic single crystals C8-BTBT.

In particular, the invention provides a preparation method of organic single crystal C8-BTBT, which comprises the following steps:

preparing and obtaining a patterned water drop structure by utilizing a photoetching method, wherein the patterned water drop structure comprises a silicon substrate and an amorphous high-transparency fluorinated polymer formed on the silicon substrate from bottom to top, the surface of the patterned water drop structure is provided with a plurality of water drop-shaped concave parts which are arrayed, and the water drop-shaped concave parts expose the silicon substrate;

C8-BTBT is dissolved in a mixed solvent system formed by mixing a good solvent and a poor solvent, so as to obtain a mixed solution of C8-BTBT;

the mixed solution is printed into the patterned water droplet structure by using an inkjet printing method to preferentially nucleate at the tip of the water droplet-shaped recess, then grow from the tip, and self-assemble and grow to fill the entire water droplet-shaped recess along a single orientation, to obtain the organic single crystal C8-BTBT.

Optionally, the fluorinated polymer is a Cytop fluorinated polymer or polytetrafluoroethylene.

Optionally, the good solvent is chlorobenzene; the poor solvent is dodecane or N, N-dimethylformamide.

Optionally, the preparing and obtaining the patterned water drop structure by using the photolithography method comprises the following steps:

spin-coating the fluorinated polymer on a silicon substrate and heating at a preset temperature for a preset time;

thermally evaporating a metal layer;

and forming photoresist on the metal layer, and carrying out photoetching by using a mask to obtain the patterned water drop structure.

Optionally, the preset temperature is any value in the range of 100-200 ℃;

the preset time is any value in the range of 10-60 min.

Optionally, the evaporation rate of the metal layer is in the range of

The thickness of the metal layer is any value in the range of 20-80 nm.

Optionally, forming a photoresist on the metal layer, and performing photolithography by using a mask to obtain the patterned water drop structure, including the following steps:

spin-coating the photoresist at 2000-5000r/min for 20-60s, and baking at 80-120deg.C for 1-5min;

exposing the substrate formed with the photoresist, the metal layer and the fluorinated polymer to ultraviolet light by using the mask, thereby performing photolithography on the photoresist;

developing in a developing solution to obtain patterned photoresist;

and removing the metal layer on the surface of the patterned photoresist and the fluorinated polymer, thereby obtaining the patterned water drop structure.

Optionally, in the step of removing the metal layer on the surface of the patterned photoresist and the fluorinated polymer, so as to obtain the patterned water drop structure, the metal layer on the surface of the photoresist is soaked and removed by using a saturated ammonium persulfate solution, and the fluorinated polymer is etched by using oxygen.

In particular, the invention also provides an organic field effect transistor comprising an organic single crystal C8-BTBT prepared by the method of any one of claims 1 to 8.

In particular, the present invention also provides an integrated circuit comprising an organic single crystal C8-BTBT prepared by the preparation method of any one of claims 1 to 8.

According to the scheme of the invention, the patterned water drop structure is obtained through preparation, and the mixed solution of the C8-BTBT is printed into the patterned water drop structure, so that the evaporation speed of the solution in each position of the pattern is effectively regulated and controlled due to the water drop structure design on the surface microstructure of the pattern, namely, the evaporation flux of the tip is far greater than that of the surrounding evaporation flux, the solution can be nucleated preferentially at the position of the tip, the effect of anchoring the organic crystal nucleation position is achieved, then the C8-BTBT grows from the tip, the whole water drop pattern grows along single-orientation self-assembly, and the organic single crystal C8-BTBT finally deposits in the water drop pattern along with the gradual evaporation of the solvent. The scheme of the invention can obtain single-oriented high-quality organic single-machine C8-BTBT. The device prepared by the organic single crystal has good repeatability and stability.

The above, as well as additional objectives, advantages, and features of the present invention will become apparent to those skilled in the art from the following detailed description of a specific embodiment of the present invention when read in conjunction with the accompanying drawings.

Drawings

Some specific embodiments of the invention will be described in detail hereinafter by way of example and not by way of limitation with reference to the accompanying drawings. The same reference numbers will be used throughout the drawings to refer to the same or like parts or portions. It will be appreciated by those skilled in the art that the drawings are not necessarily drawn to scale. In the accompanying drawings:

FIG. 1 shows a schematic flow chart of a method for producing organic single crystal C8-BTBT according to one embodiment of the present invention;

FIG. 2 shows a schematic flow chart of a method of obtaining patterned water droplet structures using photolithography preparation of step S100 in FIG. 1;

FIG. 3 shows a schematic flow chart of the method of step S130 in FIG. 2;

FIG. 4 shows a schematic block diagram of the printing of the mixed solution into the patterned water droplet structure using an inkjet printing method;

FIG. 5 shows a solvent evaporation flux graph along the line of contact of a drop-shaped recess according to one embodiment of the invention;

FIG. 6 illustrates solute concentration and velocity field distribution of a water droplet-like droplet during volatilization according to one embodiment of the invention;

FIG. 7 shows a microscopic image of an organic single crystal C8-BTBT formation process, according to one embodiment of the present invention;

FIG. 8 shows a polarized light microscope image of an organic single crystal C8-BTBT at different polarized incidence angles;

FIG. 9 shows the change in polarized reflection intensity of organic single crystal C8-BTBT at different polarized incidence angles;

FIG. 10 shows a transmission electron microscopy image of an organic single crystal C8-BTBT and a selected area electron diffraction characterization image in accordance with one embodiment of the present invention;

FIG. 11 shows a microscope image of an organic field effect transistor according to one embodiment of the invention;

FIG. 12 shows transfer characteristics of 64 organic field effect transistors according to one embodiment of the invention;

FIG. 13 shows a three-dimensional histogram of mobility of an organic field effect transistor according to one embodiment of the invention;

FIG. 14 illustrates individual mobilities and statistical numbers of threshold voltages of organic field-effect transistors according to one embodiment of the invention;

FIG. 15 shows a picture of a plurality of binary multipliers fabricated on a 1.5cm by 1.5cm silicon oxide wafer in accordance with one embodiment of the present invention;

FIG. 16 shows a photomicrograph of a single binary multiplier according to one embodiment of the invention;

FIG. 17 shows a V of a binary multiplier according to one embodiment of the invention _in -V _out Graph diagram.

Detailed Description

Fig. 1 shows a schematic flow chart of a method for producing an organic single crystal C8-BTBT according to an embodiment of the invention. As shown in fig. 1, the preparation method comprises:

step S100, preparing and obtaining a patterned water drop structure by utilizing a photoetching method, wherein the patterned water drop structure comprises a silicon substrate and an amorphous high-transparency fluorinated polymer formed on the silicon substrate from bottom to top, and the surface of the patterned water drop structure is provided with a plurality of water drop-shaped concave parts which are arrayed and arranged in an array manner, and the water drop-shaped concave parts expose the silicon substrate;

step S200, dissolving the C8-BTBT in a mixed solvent system formed by mixing a good solvent and a poor solvent to obtain a mixed solution of the C8-BTBT;

in step S300, the mixed solution is printed into the patterned water droplet structure using the inkjet printing method to preferentially nucleate at the tips of the water droplet-shaped recesses, then grow from the tips, and self-assemble and grow the entire water droplet-shaped recesses in a single orientation to obtain the organic single crystal C8-BTBT.

According to the scheme of the invention, the patterned water drop structure is obtained through preparation, and the mixed solution of the C8-BTBT is printed into the patterned water drop structure, so that the evaporation speed of the solution in each position of the pattern is effectively regulated and controlled due to the water drop structure design on the surface microstructure of the pattern, namely, the evaporation flux of the tip is far greater than that of the surrounding evaporation flux, the solution can be nucleated preferentially at the position of the tip, the effect of anchoring the organic crystal nucleation position is achieved, then the C8-BTBT grows from the tip, the whole water drop pattern grows along single-orientation self-assembly, and the organic single crystal C8-BTBT finally deposits in the water drop pattern along with the gradual evaporation of the solvent.

Fig. 2 shows a schematic flow chart of a method of obtaining patterned water droplet structures using photolithography preparation of step S100 in fig. 1. As shown in fig. 2, in the step S100, the preparation of the patterned water droplet structure by photolithography includes:

step S110, spin-coating the fluorinated polymer on the cleaned silicon substrate, and heating at a preset temperature for a preset time;

step S120, thermally evaporating a metal layer;

and step S130, forming photoresist on the metal layer, and carrying out photoetching by using a mask to obtain the patterned water drop structure.

Before step S110, the silicon substrate is further cleaned, and conventional cleaning methods in the prior art may be used. For example, the substrate is immersed in concentrated sulfuric acid at 90 ℃ for 2 hours and then sequentially ultrasonically cleaned in acetone, isopropyl alcohol and deionized water for 15 minutes each. After drying with a nitrogen stream, the substrate was further treated with an oxygen plasma cleaner (PVA, ion 40) at 100W for 300 seconds.

In step S110, the fluorinated polymer is a non-crystalline highly transparent hydrophobic material, and may be, for example, cytop fluorinated polymer or polytetrafluoroethylene. The fluorinated polymer may be spin coated, for example, at a speed of 1000 to 2000r/min for 10 to 30 seconds. Preferably, spin coating is performed at a speed of 1500r/min for 20s. The preset temperature is any one of 100 to 200 ℃, for example, 100 ℃, 150 ℃ or 200 ℃. The preset time is any value in the range of 10-60 minutes, such as 10 minutes, 30 minutes, 40 minutes, or 60 minutes. The heating process may be performed, for example, on a heating plate.

This stepIn S120, the thermal evaporation process may be performed on a thermal evaporation apparatus, for example. The evaporation rate of the metal layer is in the range of

For example, it may be +.>

Or->

The thickness of the metal layer is in the range of any one of 20-80nm, such as 20nm, 40nnm, 60nm or 80nm. The material of the metal layer may be copper, for example.

Fig. 3 shows a schematic flow chart of the method of step S130 in fig. 2. As shown in fig. 3, the step S130 includes:

step S131, spin-coating the photoresist at the speed of 2000-5000r/min for 20-60S, and baking at the temperature of 80-120 ℃ for 1-5min;

step S132, exposing the substrate formed with the photoresist, the metal layer and the fluorinated polymer to ultraviolet light by using a mask, thereby performing photolithography on the photoresist;

step S133, developing in a developing solution to obtain patterned photoresist;

step S134, removing the metal layer and the fluorinated polymer on the surface of the patterned photoresist, thereby obtaining the patterned water drop structure.

In step S131, the photoresist is AR-P5350 type photoresist. The spin-coating speed of the photoresist may be, for example, 2000r/min, 3000r/min, 4000r/min or 5000r/min, or any other value from 2000 to 5000 r/min. The spin coating time may be, for example, 20s, 40s, 50s or 60s, or any other value from 20 to 60 s. The baking temperature may be, for example, 80 ℃, 100 ℃ or 120 ℃, or any other value from 80 to 120 ℃. The baking time may be, for example, 1min, 2min, 3min, 4min or 5min, or any other value of 1 to 5 min.

In this step S132, the irradiation time under ultraviolet light is any one of 1 to 2S, for example, 1S, 1.5S, 1.8S, or 2S. In this step S133, the development time in the developer is, for example, any one of 5 to 10S, for example, 5S, 8S, or 10S.

In the step S134, the metal layer on the photoresist surface is removed by soaking in a saturated ammonium persulfate solution, and the fluorinated polymer is etched away by using oxygen gas by using a reactive ion etching machine.

In step S200, the good solvent is chlorobenzene; the poor solvent is dodecane or N, N-dimethylformamide. The good solvent has a boiling point lower than the poor solvent so that the good solvent in which the material is dissolved will preferentially vaporize to nucleate at the tip. In addition, the surface tension of the poor solvent is smaller than that of the good solvent, so that the poor solvent with higher concentration can be continuously supplemented below the liquid level as the good solvent evaporates, and a flat liquid level is provided for the material to realize stable growth.

Fig. 4 shows a schematic block diagram of the printing of the mixed solution into the patterned water droplet structure using an inkjet printing method. As shown in fig. 4, the mixed solution of C8-BTBT is applied to the droplet-shaped recess. The printer head is spaced from the drop-shaped recess by a suitable distance.

Fig. 5 shows a solvent evaporation flux profile along the line of contact of a drop-shaped recess according to one embodiment of the invention. As shown in fig. 5, the tip portion of the droplet-shaped concave portion is the largest in volatilization flux. FIG. 6 illustrates solute concentration and velocity field distribution of a droplet of water drop-like droplets during volatilization according to one embodiment of the invention.

Fig. 7 shows a microscopic image of an organic single crystal C8-BTBT formation process according to an embodiment of the invention. As shown in fig. 7, nucleation and crystallization processes are from i to iv, and poor solvent evaporation processes are from v to vi.

Fig. 8 shows a polarized light microscope image of the organic single crystal C8-BTBT at different polarized light incidence angles. Fig. 9 shows the change in polarized reflection intensity of the organic single crystal C8-BTBT at different polarized incidence angles. As can be seen from fig. 8 and 9, the organic single crystal C8-BTBT prepared by the present invention has a single growth orientation.

In order to further characterize the crystallization quality of the organic single crystal C8-BTBT, transmission electron diffraction (TEM) selective electron diffraction characterization is performed on the organic single crystal C8-BTBT. FIG. 10 shows a transmission electron microscope image of an organic single crystal C8-BTBT and a selected area electron diffraction characterization image, in accordance with one embodiment of the present invention. Fig. 10 (a) shows that the material in one droplet shape exhibits a uniform distribution (black areas within the droplet shape are copper mesh used for preparing TEM samples). In fig. 10 (b), a selective electron diffraction pattern (SAED) of a selected area, it can be seen that five different areas of any selected area in a water droplet can exhibit uniform diffraction lattices, which are different from diffraction rings of a polycrystalline sample, so that it can be demonstrated that the C8-BTBT prepared by the present invention has excellent single crystal properties.

In particular, the embodiment of the invention also provides an organic field effect transistor. The organic field effect transistor comprises the organic single crystal C8-BTBT. Fig. 11 shows a microscope image of an organic field effect transistor according to one embodiment of the invention. The organic field effect transistor is an 8×8 organic field effect transistor array obtained by thermal evaporation, and comprises placing metal mask for aligning source and drain electrodes on top of the transistor array, and maintaining

Is thermally evaporated at a rate of 50nm Ag, followed by +.>

1.5nm F4-TCNQ. The channel length and effective width of the mask were 100 microns and 80 microns, respectively.

Fig. 12 shows transfer characteristics of 64 organic field effect transistors according to one embodiment of the present invention. As can be seen from FIG. 12, the highest mobility of the device is up to 17.3cm ² V ^-1 s ^-1 The average mobility can reach 12.5cm ² V ^-1 s ^-1 . Fig. 13 shows a three-dimensional histogram of mobility of an organic field effect transistor according to one embodiment of the invention. As can be seen from fig. 13, the device performance was uniformly distributed, and the coefficient of variation of the mobility of the device was calculated to be 16.7%, which can be an illustration of the uniformity of the device performance. FIG. 14 shows an organic field effect crystal according to one embodiment of the inventionStatistics of individual mobilities and threshold voltages of the tube. As can be seen, the vast majority of devices have mobility in excess of 10cm ² V ^-1 s ^-1 And the threshold voltage does not exceed-2V, further illustrating that the devices all exhibit good performance. All electrical property characterizations were measured using a Keithley 4200-SCS semiconductor analyzer in an air environment.

In particular, the invention also provides an integrated circuit comprising the organic single crystal C8-BTBT. In one embodiment, the integrated circuit may be, for example, a binary multiplier. FIG. 15 shows a picture of a plurality of binary multipliers fabricated on a 1.5cm by 1.5cm silicon oxide wafer in accordance with one embodiment of the present invention. Fig. 16 shows a photomicrograph of a single binary multiplier according to one embodiment of the present invention. FIG. 17 shows a V of a binary multiplier according to one embodiment of the invention _in -V _out Graph diagram. As can be seen from fig. 17, V _in -V _out The curve exhibits normal multiplication logic, indicating that all devices are operating properly.

In one embodiment, the binary multiplier is prepared by: the Ag bottom electrode is cleaned by photoetching and Lift-off process on SiO ₂ An electrode pattern is formed on the Si substrate. The Ag bottom electrode consists of a square area and a rectangular area connected with the square area. Then, SU-8 photoresist is spin-coated on the substrate on which the Ag bottom electrode is deposited, and soft baking is performed to form a dielectric layer. Subsequently, SU-8 photoresist over the square area of Ag electrode is selectively removed by photolithography to form a via hole for further electrical connection. Then, according to the method for preparing the patterned water droplet structure, the patterned water droplet structure is arranged on the Ag bottom electrode in the rectangular area. Next, patterned C8-BTBT single crystals were inkjet printed on these patterned drop structures. Finally, ag top electrodes are deposited on the C8-BTBT monocrystal through the heat evaporation of the aligned metal mask plates, and the preparation of the binary multiplier is completed. Wherein the evaporation rates of the Ag bottom electrode and the Ag top electrode are respectively

By now it should be appreciated by those skilled in the art that while a number of exemplary embodiments of the invention have been shown and described in detail herein, many other variations or modifications of the general principles of the invention may be directly ascertained or inferred from the present disclosure without departing from the spirit and scope of the invention. Accordingly, the scope of the present invention should be understood and deemed to cover all such other variations or modifications.

Claims

1. The preparation method of the organic single crystal C8-BTBT is characterized by comprising the following steps:

2. The method of claim 1, wherein the fluorinated polymer is a Cytop fluorinated polymer or polytetrafluoroethylene.

3. The method according to claim 2, wherein the good solvent is chlorobenzene; the poor solvent is dodecane or N, N-dimethylformamide.

4. A method of preparing a patterned water droplet structure according to any one of claims 1-3, wherein the preparing using photolithography comprises the steps of:

thermally evaporating a metal layer;

5. The method according to claim 4, wherein the preset temperature is any one value in the range of 100 to 200 ℃;

the preset time is any value in the range of 10-60 min.

6. The method of claim 4, wherein the metal layer has an evaporation rate in the range of

The thickness of the metal layer is any value in the range of 20-80 nm.

7. The method of claim 4, wherein forming a photoresist on the metal layer and performing photolithography using a mask to obtain the patterned water droplet structure comprises the steps of:

developing in a developing solution to obtain patterned photoresist;

8. The method of claim 7, wherein in the step of removing the metal layer on the patterned photoresist surface and the fluorinated polymer to obtain the patterned water droplet structure, the metal layer on the photoresist surface is removed by soaking in a saturated ammonium persulfate solution, and the fluorinated polymer is etched away by oxygen.

9. An organic field effect transistor comprising an organic single crystal C8-BTBT prepared by the method of any one of claims 1-8.

10. An integrated circuit comprising an organic single crystal C8-BTBT prepared by the method of any one of claims 1-8.