Application of an organic semiconductor single crystal in an organic semiconductor device

Abstract

The present invention provides an application of an organic semiconductor single crystal in an organic semiconductor device. The orange-phase PBNA single crystal of the present invention has a special lattice distortion structure, which enables it to exhibit low-temperature transport characteristics in a field-effect transistor. When used as an active layer in a single crystal device, it exhibits a significant negative correlation with temperature during temperature-dependent testing, demonstrating the great potential of this material in practical applications.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic semiconductor materials, and in particular relates to an application of an organic semiconductor single crystal in an organic semiconductor device. Background Art

[0002] Since Tsumura's group first reported the use of polythiophene conductive polymers to fabricate organic field-effect transistors (OFETs) in 1987, over a decade of continuous research in organic optoelectronics and other fields has significantly improved the device performance of OFETs, while also significantly advancing their stability and versatility. Currently, many field-effect transistors have entered the market, but most are amorphous thin-film transistors. Their inherent molecular disorder leads to numerous drawbacks, such as low carrier mobility and poor structural stability, which in turn results in poor device performance.

[0003] Compared to organic thin-film transistors, organic single-crystal field-effect transistors offer significant advantages. The orderly molecular arrangement within organic single crystals allows for continuous device performance in a single direction. The absence of phase boundaries and low impurity content in organic single crystals, combined with minimal defects, effectively prevent the efficiency roll-off seen in thin-film transistors. Given their unique molecular stacking and arrangement, organic single crystals hold significant practical significance for studying the mechanisms of organic optoelectronic processes.

[0004] The organic field-effect transistor (OFET) is a three-electrode system consisting of a source, a drain, and a gate. Normally, the source is grounded (Vs=0V), and the operation of the OFET device is controlled by the drain voltage (Vg) and the gate voltage (Vg). In addition to the electrodes, the OFET also includes an organic semiconductor layer and an insulating layer. The organic semiconductor layer, as the core part of the OFET, plays a decisive role in the performance of the device. Unlike conventional inorganic semiconductors, organic semiconductors usually only allow single carrier propagation due to their own structural limitations, which seriously hinders the development of organic semiconductors in electronic circuits. Summary of the Invention

[0005] The present invention aims to address at least one of the technical problems existing in the aforementioned prior art. To this end, in a first aspect, the present invention proposes the use of an orange-phase PBNA ((2Z,2'Z)-3,3'-(1,4-phenylene)bis(2-(naphthalene-2-yl)acrylonitrile)) single crystal in organic semiconductor devices. This orange-phase PBNA single crystal possesses a unique lattice distortion structure, resulting in low-temperature transport properties in field-effect transistors.

[0006] A second aspect of the present invention provides an organic semiconductor device comprising the orange-phase PBNA single crystal.

[0007] According to a first aspect of the present invention, an orange-phase PBNA single crystal is used in an organic semiconductor device. The orange-phase PBNA single crystal is a monoclinic crystal with a space group of I2 / a. The structural formula of the PBNA in the orange-phase PBNA single crystal is shown in Formula I:

[0008]

[0009] In some embodiments of the present invention, the unit cell parameters of the orange phase PBNA single crystal are: α=90°, β=110.403°, γ=90°.

[0010] In some preferred embodiments of the present invention, the orange-phase PBNA single crystal comprises a first isomer and a second isomer. The twist angles between the plane containing the central benzene ring of the first isomer and the plane containing the naphthalene rings at both ends are 3.33° and 1.48°, respectively; the twist angles between the plane containing the central benzene ring of the second isomer and the plane containing the naphthalene rings at both ends are 23.58° and 23.18°, respectively. Schematic diagrams of the structures of the first isomer and the second isomer are as follows:

[0011]

[0012] In some more preferred embodiments of the present invention, the orange-phase PBNA single crystal is formed by the interaction between the first isomer and the second isomer molecules, and the molar ratio of the first isomer to the second isomer is 2:1.

[0013] In some more preferred embodiments of the present invention, the interaction comprises at least one of van der Waals force, hydrogen bond, halogen bond or aromatic ring-aromatic ring (such as CH...π and π-π bonds, etc.) interaction.

[0014] In some more preferred embodiments of the present invention, the organic semiconductor device is selected from an organic single crystal field effect transistor or an organic single crystal light emitting field effect transistor.

[0015] In some more preferred embodiments of the present invention, the organic semiconductor layer of the organic semiconductor device includes the orange-phase PBNA single crystal.

[0016] In some more preferred embodiments of the present invention, the organic semiconductor layer is an organic single crystal layer.

[0017] According to a second aspect of the present invention, an organic semiconductor device is provided, comprising the orange-phase PBNA single crystal.

[0018] In some embodiments of the present invention, the organic semiconductor device is selected from an organic single crystal field effect transistor or an organic single crystal light emitting field effect transistor.

[0019] In some preferred embodiments of the present invention, the organic semiconductor layer of the organic semiconductor device includes the orange-phase PBNA single crystal.

[0020] In some preferred embodiments of the present invention, the organic semiconductor layer is an organic single crystal layer.

[0021] The beneficial effects of the present invention are:

[0022] 1. The orange-phase PBNA single crystal of the present invention has a special lattice distortion structure, which makes it exhibit transport characteristics under low temperature conditions. When used as an organic semiconductor layer in an organic single crystal field effect transistor, it exhibits bipolar transmission performance, and the mobility of the single crystal device can reach up to μ e =0.22cm 2 V -1 s -1 (Electronics), μ h =1.37cm 2 V -1 s -1 (hole).

[0023] 2. In the present invention, when the orange-phase PBNA single crystal is used as an organic semiconductor layer in an organic single crystal field effect transistor, it has a low threshold voltage, V th,e =18.0V(electron), V th,p =-9.3V(hole).

[0024] 3. In the present invention, when the orange-phase PBNA single crystal is used as an organic semiconductor layer in a single crystal device, it shows an obvious negative correlation with temperature during the temperature dependence test process. This shows the great potential of this material in practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0026] Figure 1 This is an image of the orange-phase PBNA crystals in Example 2 of the present invention under an ultraviolet fluorescence microscope.

[0027] Figure 2 The molecular conformation diagram (a) and unit cell diagram (b) of the green phase PBNA crystal of the present invention and the molecular conformation diagram (c) and unit cell diagram (d) of the orange phase PBNA crystal.

[0028] Figure 3 Schematic diagram of the structure of the organic single crystal field effect transistor device based on PBNA orange phase crystal in Example 3.

[0029] Figure 4(a) and (b) the orange-phase PBNA crystal hole OFET device in Example 3.

[0030] Figure 5 These are the transfer (a) and output (b) curves of the orange-phase PBNA single crystal hole field-effect transistor and the transfer (c) and output (d) curves of the electron field-effect transistor in Experimental Example 1.

[0031] Figure 6 The transfer (a) and output (b) curves of the green phase PBNA single crystal hole field effect transistor and the transfer (c) and output (d) curves of the electron field effect transistor.

[0032] Figure 7 Schematic diagram of the device temperature control device in Experimental Example 2.

[0033] Figure 8 These are the images of the changes in the mobility and threshold voltage of the hole field effect transistor of the orange phase PBNA crystal (a) and the green phase PBNA crystal (c) with temperature in Experimental Example 2, and the images of the changes in the mobility and threshold voltage of the electron field effect transistor of the orange phase PBNA crystal (b) and the green phase PBNA crystal (d) with temperature. DETAILED DESCRIPTION

[0034] The following will clearly and completely describe the concept and technical effects of the present invention in conjunction with the embodiments to fully understand the purpose, features and effects of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0035] Example 1

[0036] In this example, PBNA was prepared, and the specific process was as follows:

[0037] S1: In a 25 mL round-bottom flask, 134.1 mg (1 mmol) of terephthalaldehyde and 334.4 mg (2 mmol) of 2-naphthylacetonitrile were weighed, 5 mL of tetrahydrofuran and 10 mL of tert-butanol were added to dissolve all the solids, and the mixture was refrigerated and vacuumed with N2 three times to remove all air from the flask.

[0038] S2: Heat in a water bath at 46°C under an N2 atmosphere. After 30 minutes, quickly add 0.25 mL of 1 M potassium tert-butoxide and 0.3 mL of 1 M tetrabutylammonium hydroxide to the flask and continue stirring vigorously for approximately 30 minutes. After the reaction is complete, pour the mixed solution into 40 mL of methanol acidified with two drops of acetic acid. An orange-yellow solid will immediately precipitate. The precipitated solid is filtered and purified by column chromatography using a 1:1 volume ratio of dichloromethane to petroleum ether as the developing solvent. PBNA is obtained.

[0039] Example 2

[0040] This embodiment adopts the physical vapor transmission method to grow orange-phase PBNA crystals. The specific process is as follows:

[0041] S1: Take a small amount of PBNA sample and place it in a quartz tube, align it with the sublimation zone of the tube furnace, connect the gas line, purge the pipe with inert gas, and maintain the three-stage temperature in the furnace at around 100°C for a period of time to completely remove the water vapor inside the sample and in the air;

[0042] S2: Precisely controlling the temperatures in the sublimation, growth, and cooling zones of the tube furnace, as well as the inert gas flow rate and growth time, ultimately yielded PBNA crystals at (285°C, 230°C, 230°C, 40 sccm / 3d). This yielded a coexistence of green and orange PBNA phases. Lowering the temperatures in the growth and cooling zones ultimately yielded single-phase orange crystals at (285°C, 229°C, 229°C, 40 sccm / 3d).

[0043] The image of orange phase PBNA crystal under ultraviolet fluorescence microscope is as follows Figure 1 shown.

[0044] from Figure 1 It can be seen that the orange-phase PBNA crystals emit orange light under ultraviolet fluorescence.

[0045] Mercury software was used to analyze and observe the structures of orange-phase PBNA single crystals and green-phase PBNA single crystals. The molecular conformation diagram (a) and unit cell diagram (b) of the green-phase PBNA crystal and the molecular conformation diagram (c) and unit cell diagram (d) of the orange-phase PBNA crystal are shown in the figure. Figure 2 shown.

[0046] Figure 2Analysis shows that PBNA molecules in the green phase crystals exist in a trans configuration, resulting in a small unit cell structure, with each unit cell consisting of four complete PBNA molecules. In the orange phase crystals, there are two types of molecules, A and B, which are stacked in a mixed manner throughout the crystal structure, resulting in a larger unit cell structure in the orange phase crystals, with each unit cell consisting of 20 complete PBNA molecules. Due to the special structure of the orange phase crystals, the intermolecular interactions within the orange phase crystals are more abundant, which leads to the superior hole transport properties of the orange phase PBNA crystals, which are an order of magnitude higher than those of the green phase PBNA crystals.

[0047] Example 3

[0048] Schematic diagram of the structure of an organic single crystal field effect transistor device Figure 3 As shown, this embodiment prepares an organic single crystal field effect transistor device, and the specific process is as follows:

[0049] S1: Si / SiO2 substrate cutting. The silicon wafer used in the preparation of organic single crystal field effect transistors is imported from Japan, with a bottom conductivity of 0.002~0.005Ωcm -1 A 200nm SiO2 dielectric layer is grown on top of the conductive silicon. The 6-inch is divided into 1×1cm with a diamond cutter. 2 After placing the substrate, use a scraper to scrape off the SiO2 layer at both ends of the wafer to facilitate device testing.

[0050] S2: Si / SiO2 substrate cleaning. Place the Si / SiO2 glass substrate on an ITO holder and use an ultrasonic cleaner to clean it. Use dichloromethane, ethanol, and acetone in this order, each for 15 minutes, three times. This is to thoroughly remove any remaining contaminants on the Si / SiO2 substrate, such as photoresist, dust, and grease, and to improve interfacial contact. The substrate is then dried in a vacuum oven.

[0051] S3: Remove a portion of the Si / SiO2 substrate and soak it in a saturated piranha solution of concentrated sulfuric acid and hydrogen peroxide (7:3 by volume) for 15 minutes. This further modifies the silicon wafer surface to facilitate the next step of dielectric layer assembly. Rinse with distilled water and dry until ready for use.

[0052] S4: Place the treated Si / SiO2 substrate in an oxygen plasma etcher and bombard it with oxygen plasma (O2Plasma) for 120s to completely remove any residual organic matter on the surface of the ITO glass substrate.

[0053] S5: The substrate was transferred to a nitrogen-filled glove box and placed on a hot plate maintained at 50°C. An 80nm thick layer of polymethyl methacrylate (PMMA) / perfluororesin (CYTOP) was spin-coated, followed by annealing on a 180°C / 100°C hot plate for 1 hour. The orange-phase PBNA crystals obtained by the physical vapor transfer method in Example 2 were electrostatically transferred to the dielectric layer using a brush. The substrate was then placed in the slot of the evaporation apparatus and placed upside down in the evaporation chamber. The water and oxygen content in the glove box remained below 0.1ppm throughout the entire process.

[0054] S6: In the vacuum deposition chamber, the -4 A 1.5nm thick layer of cesium fluoride (CsF) / molybdenum oxide (MoO3) was first deposited on the organic film under a vacuum of 1.5 Pa to facilitate electron / hole injection. A 150nm thick layer of calcium (Ca) / gold (Au) electrode was then deposited on the CsF / MoO3. The thickness of the metal layer was measured using a quartz crystal thickness gauge during the deposition process. After deposition, the film was removed and tested using a Keyence VHX-900F instrument.

[0055] like Figure 4 As shown, two device structures were prepared: the symmetrical Au electrode single crystal OFET device structure was Si / SiO2 / CYTOP (80nm) / MoO3 (1.5nm) / Au (150nm) (Figure (a)); the symmetrical Ca electrode single crystal OFET device structure was Si / SiO2 / PMMA (80nm) / Ca (150nm) (Figure (b)).

[0056] Test Example 1

[0057] This test example tests the performance of an organic single crystal field effect transistor device. The specific process is as follows:

[0058] The performance of field effect transistors is evaluated by parameters such as carrier mobility, threshold voltage, and subthreshold swing. For the measurement of mobility, the asymptotic channel approximation is used, and the saturation region formula is used. It can be calculated. DS is the source-drain current, V G is the gate voltage, C ox is the capacitance per unit area of the insulating layer.

[0059] During the transfer curve test, the source-drain voltage V DS At -70V (holes) / 70V (electrons), the change V G Get Ids~V G ; During the output curve test, fix V G , change V DS Get Ids~V DS , in order to express the switching state of the transistor, let VG Seven curves are obtained from -10 to -70 V (holes) / 10 V to 70 V (electrons).

[0060] The transfer (a) and output (b) curves of the orange phase PBNA single crystal hole field effect transistor and the transfer (c) and output (d) curves of the electron field effect transistor are shown in Figure 2. Figure 5 shown.

[0061] Green phase PBNA single crystal hole field effect transistor and electron field effect transistor were prepared at the same time. According to the same test range, the transfer (a) and output (b) curves of the green phase PBNA single crystal hole field effect transistor and the transfer (c) and output (d) curves of the electron field effect transistor were obtained as shown in the figure. Figure 6 shown.

[0062] Figure 5 Analysis shows that the hole mobility of PBNA orange phase single crystal is ~1.37cm 2 V -1 s -1 , turn-on voltage ~ -9.3V, subthreshold swing ~ 0.57V dec -1 The electron mobility of PBNA orange phase single crystal is ~0.22cm2 V -1 s -1 , turn-on voltage ~18.0V, subthreshold swing ~1.49V dec -1 It can be seen that the PBNA single crystal field effect transistor has excellent double-click transmission properties.

[0063] Figure 6 Analysis shows that the hole mobility of PBNA green phase single crystal is 0.08 cm 2 V -1 s -1 , turn-on voltage ~ -5.2V, subthreshold swing ~ 7.20V dec -1 The electron mobility of PBNA green phase single crystal is ~0.29cm 2 V -1 s -1 , turn-on voltage ~25.0V, subthreshold swing ~0.48V dec -1 As can be seen, the green-phase PBNA single-crystal field-effect transistor also exhibits bipolar transport properties. Compared to the orange-phase PBNA, the green-phase crystal has a slightly higher electron mobility but a much lower hole transport characteristic than the orange-phase crystal.

[0064] Test Example 2

[0065] This test example tests the low-temperature performance of an organic single-crystal field-effect transistor device. The specific process is as follows:

[0066] Build a low temperature test system, the device diagram is as follows Figure 7 As shown in the figure, the operating principle is as follows: high-purity nitrogen gas entering the glove box is cooled by a chiller before being heated and controlled by a thermocouple at the outlet. The temperature-controlled gas is then blown across the device surface to achieve temperature control. To ensure the most accurate device temperature possible, a temperature probe is attached to the side of the test bench for temperature calibration.

[0067] The images of the mobility and threshold voltage of the hole field effect transistor of the orange phase and green phase PBNA crystals as a function of temperature (a) (c) and the images of the mobility and threshold voltage of the electron field effect transistor as a function of temperature (b) (d) are shown in the figure. Figure 8 shown.

[0068] Figure 8 Analysis shows that single-crystal field-effect transistors made from orange-phase PBNA crystals of both device structures exhibit identical behavior at low temperatures. The hole mobility of the orange-phase PBNA device increases with decreasing temperature, while the electron mobility also increases with decreasing temperature. This differs from conventional organic semiconductors and demonstrates the superior properties of orange-phase PBNA crystals.

[0069] Green-phase PBNA single-crystal field-effect transistor devices exhibit similar performance trends at low temperatures. As the temperature decreases, the mobility of both holes and electrons in the green-phase crystal decreases simultaneously, consistent with the mobility-temperature variation trend of conventional organic semiconductors. This indirectly demonstrates the uniqueness of the orange-phase PBNA crystal.

[0070] While the embodiments of the present invention have been described in detail above, the present invention is not limited to the embodiments described above. Various modifications may be made within the scope of knowledge possessed by a person skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof may be combined with one another unless there is a conflict.

Claims

1. An orange-phase PBNA single crystal is used in an organic semiconductor layer of an organic single crystal field effect transistor under low temperature conditions, characterized in that: The low temperature conditions are 270K, 280K, 290K, and 300K; the orange-phase PBNA single crystal is a monoclinic crystal with a space group of I 2 / a. The structural formula of PBNA in the orange-phase PBNA single crystal is shown in Formula I:

2. The use according to claim 1, characterized in that: The unit cell parameters of the orange phase PBNA single crystal are: α=90°, β=110.403°, γ=90°.

3. The use according to claim 1, characterized in that: The orange-phase PBNA single crystal includes a first isomer and a second isomer. The twist angles of the plane where the central benzene ring of the first isomer is located and the plane where the naphthalene rings at both ends are located are 3.33° and 1.48°, respectively; the twist angles of the plane where the central benzene ring of the second isomer is located and the plane where the naphthalene rings at both ends are located are 23.58° and 23.18°, respectively.

4. The use according to claim 3, characterized in that: The orange-phase PBNA single crystal is formed by the interaction between the first isomer and the second isomer molecules, and the molar ratio of the first isomer to the second isomer is 2:1.

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