Preparation process of flexible planar heterojunction near-infrared photoelectric detector

Abstract

The invention discloses a preparation process of a flexible planar heterojunction near-infrared photoelectric detector, and belongs to the technical field of photoelectric detectors, the structure of the detector is PET / I TO / PEDOT: PSS / optical active material layer / C60 / Al, and the preparation process comprises the following steps: a) placing a PET / ITO substrate in an oxygen plasma cleaning machine to carry out plasma treatment on the surface; b) spin-coating the PEDOT: PSS solution filtered by the nylon filter membrane on a substrate, and annealing to obtain a hole transport layer film; c) spin-coating a photoactive material solution in a nitrogen environment and annealing; and d) under a vacuum condition, sequentially depositing C60 and Al with different thicknesses through the patterned mask plate to form an effective detection area. The near-infrared photoelectric detector capable of being used for monitoring the heart rate of the human body is prepared through a simple and efficient planar heterojunction preparation process, and excellent device stability is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of photodetectors, and particularly to a preparation process of a flexible planar heterojunction type near-infrared photodetector. Background Art

[0002] Flexible diode-type near-infrared organic photodetectors (NIR-OPDs) can convert optical or non-optical parameters into visual electrical signals by detecting near-infrared light invisible to the human eye, and are widely used in sensing fields such as bionic eye devices, health monitoring, communication technologies, and spectral analysis.

[0003] In order to separate singlet excitons into charges, the active layer of diode-type OPDs is usually a donor-acceptor (D-A) heterojunction, that is, a semiconductor with charge transport characteristics opposite to those of the photoactive material needs to be matched. On the one hand, it forms the built-in electric field and contact interface required for exciton dissociation, and on the other hand, it provides a carrier transport channel. According to the mixing form of the donor and acceptor components, the active layer can be divided into planar heterojunction (PHJ), bulk heterojunction (BHJ), and planar-bulk composite heterojunction (P-BHJ).

[0004] Both flexible BHJ and P-BHJ involve thin films formed by mixing donor and acceptor materials. In the preparation process of this type of device, the preparation process and conditions need to be strictly set according to the mutual solubility and energy level matching of the D and A components. Its processing technology covers complicated processes such as solvent selection, heating, stirring, concentration control, and filtration of insoluble substances, which greatly increases labor consumption, and the components restrict each other, limiting the functional development of the device. At the same time, its performance is strongly affected by the mixing form of the donor and acceptor in the active layer. Domains of different sizes affect the exciton dissociation effect, and there are also problems such as poor batch repeatability and solvent and additive dependence. On the other hand, the D and A components are distributed throughout the active layer, increasing the probability of direct contact with the two end electrodes and the opposite charge transport layer, resulting in a low injection barrier and a high leakage current, making it difficult for the device to achieve low dark current and high specific detectivity. In addition, the inherently low miscibility of the D and A materials makes the interpenetrating network phase of the BHJ usually in a metastable state and prone to phase separation. The distributed tiny p-n junctions also generate a high density of carrier traps, making the stability of the device poor.

[0005] Therefore, it is a problem to be solved at present to prepare a flexible planar heterojunction type near-infrared photodetector with a simple process, high stability, and excellent detection performance. Summary of the Invention

[0006] The purpose of the present invention is to provide a preparation process of a flexible planar heterojunction type near-infrared photodetector to solve the above problems.

[0007] To achieve the above object, the present invention provides a preparation process of a flexible planar heterojunction type near-infrared photodetector. The structure of the detector is PET / ITO / PEDOT:PSS / photoactive material layer / C60 / Al, and its preparation process specifically includes the following steps:

[0008] a) Place the PET / ITO substrate in an oxygen plasma cleaner for plasma treatment of the surface;

[0009] b) Subsequently, spin-coat the PEDOT:PSS solution filtered through a nylon filter membrane on the substrate, anneal to obtain a hole transport layer thin film, and transfer it to a nitrogen glove box for standby;

[0010] c) Spin-coat the photoactive material solution and anneal it under a nitrogen environment;

[0011] d) Under vacuum conditions, deposit C60 and Al with different thicknesses in sequence through a patterned mask to form an effective detection area.

[0012] Preferably, in the above preparation process of a flexible planar heterojunction type near-infrared photodetector, the photoactive material layer is a compound represented by the following general formula: C 96+x H 110+y N m O4S n , where x is 0 - 10, y is 0 - 6, m is 4 or 6, and n is 5 or 7.

[0013] Preferably, in the above preparation process of a flexible planar heterojunction type near-infrared photodetector, in step a), the power of the oxygen plasma treatment is 100 - 300 W, and the treatment time is 10 minutes.

[0014] Preferably, in the above preparation process of a flexible planar heterojunction type near-infrared photodetector, in step b), the thickness of the hole transport layer thin film is 30 - 50 nm. Spin-coat the PEDOT:PSS solution at a speed of 3000 rpm and anneal it at 150 °C for 10 minutes to obtain the hole transport layer thin film.

[0015] Preferably, in the above preparation process of a flexible planar heterojunction type near-infrared photodetector, in step c), the photoactive material layer is prepared by spin-coating the solution at a concentration of 4 - 20 mg / mL at a speed of 2500 rpm and annealing it at 80 °C for 10 minutes.

[0016] Preferably, in the above preparation process of a flexible planar heterojunction type near-infrared photodetector, in step d), the thickness of the C60 layer is 20 - 50 nm, and the thickness of the Al layer is 100 - 200 nm. Both are prepared by vacuum evaporation process, and the vacuum degree ≤ 6×10 -4 Pa.

[0017] Preferably, in the preparation process of the above-mentioned flexible planar heterojunction type near-infrared photodetector, the effective area of the detector is 0.35 cm 2 .

[0018] Therefore, the present invention adopts the preparation process of a flexible planar heterojunction type near-infrared photodetector with the above structure, and prepares a near-infrared photodetector that can be used for human heart rate monitoring through a simple and efficient planar heterojunction preparation process, and excellent device stability is obtained. A streamlined and efficient planar heterojunction diode structure is adopted, which can effectively reduce the complexity of device preparation, save preparation costs and time. The prepared near-infrared photodetector has a light response range covering the visible light-near-infrared region, the detectable wavelength range exceeds 1.3 microns, and the photoactive material is applied to the flexible OPD device, and a specific detectivity of more than 10 12 Jones can be achieved in the near-infrared region >1.1 μm, which has broken through the detection limit of commercially available silicon photodetectors, and the dark current density is at 10 -10 A cm -2 order of magnitude, and the human pulse frequency can be accurately measured under light irradiation of different wavelengths.

[0019] The technical solution of the present invention will be further described in detail below with reference to the drawings and embodiments. Description of the Drawings

[0020] Figure 1 Schematic diagram of the bending parameters of the flexible planar heterojunction type near-infrared photodetector of the present invention;

[0021] Figure 2 Relationship curve diagram of the specific detectivity (D*) and wavelength of the flexible planar heterojunction type near-infrared photodetector of the present invention;

[0022] Figure 3 Comparison diagram of the responsivity of the flexible planar heterojunction type near-infrared photodetector of the present invention changing with the bending diameter;

[0023] Figure 4 Schematic diagram of the dark current density of the flexible planar heterojunction type near-infrared photodetector of the present invention;

[0024] Figure 5 PPG waveform diagram of the flexible planar heterojunction type near-infrared photodetector of the present invention. Detailed Embodiments

[0025] To better understand the above technical solution, the following will provide a detailed description of the above technical solution in combination with the accompanying drawings of the specification and specific implementation manners. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0026] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "the", and "said" used in the embodiments of the present invention and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise. "Plural" generally includes at least two.

[0027] It should also be noted that the term "comprises", "comprising", or any other variation thereof is intended to cover a non-exclusive inclusion, such that a commodity or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such commodity or device. Without further limitation, the element defined by the statement "comprising an..." does not exclude the existence of additional identical elements in the commodity or device including the element.

[0028] The present invention provides a preparation process for a flexible planar heterojunction near-infrared photodetector. The structure of the detector is PET / ITO / PEDOT:PSS / photoactive material layer / C60 / Al. The preparation process specifically includes the following steps:

[0029] a) Place the PET / ITO substrate in an oxygen plasma cleaner for plasma treatment of the surface;

[0030] b) Subsequently, spin-coat the PEDOT:PSS solution filtered through a nylon filter membrane on the substrate, and obtain a hole transport layer thin film after annealing, and transfer it to a nitrogen glove box for standby;

[0031] c) Spin-coat the photoactive material solution and anneal it under a nitrogen atmosphere;

[0032] d) Under vacuum conditions, deposit C60 and Al with different thicknesses in sequence through a patterned mask to form an effective detection area.

[0033] To further optimize the above technical solution, the photoactive material layer is a compound represented by the following general formula: C 96+ x H 110+y N m O4S n, where x is from 0 to 10, y is from 0 to 6, m is 4 or 6, and n is 5 or 7; preferably C 100 H 116 N6O4S5, C 106 H 114 N6O4S7, C 96 H 110 One of N4O4S5.

[0034] To further optimize the above technical solution, the power of the oxygen plasma treatment in step a) is 100 - 300 W, and the treatment time is 10 minutes.

[0035] To further optimize the above technical solution, the hole transport layer film in step b) has a thickness of 30 - 50 nm, and the PEDOT:PSS solution is spin-coated at a speed of 3000 rpm and annealed at 150 °C for 10 minutes to obtain the hole transport layer film.

[0036] To further optimize the above technical solution, the photoactive material layer in step c) is prepared by spin-coating the solution at a concentration of 4 - 20 mg / mL at a speed of 2500 rpm and annealed at 80 °C for 10 minutes.

[0037] To further optimize the above technical solution, the thickness of the C60 layer in step d) is 20 - 50 nm, and the thickness of the Al layer is 100 - 200 nm, both prepared by vacuum evaporation process, with the vacuum degree ≤ 6×10 -4 Pa.

[0038] To further optimize the above technical solution, the effective area of the detector is 0.35 cm 2 .

[0039] To introduce the preparation process of a flexible planar heterojunction type near-infrared photodetector provided by the embodiments of the present invention more clearly and in detail, the following will be described in combination with specific embodiments.

[0040] Example 1

[0041] Prepare a device structure of PET / ITO / PEDOT:PSS / C 100 H 116 N6O4S5 / C60 / Al. Place the PET / ITO substrate in an oxygen plasma cleaner for 10 min of plasma treatment on the surface; then spin-coat the PEDOT:PSS solution filtered through a nylon filter membrane on the ITO substrate at a speed of 3000 rpm, and obtain the hole transport layer film (HTL) after 10 min of thermal annealing at 150 °C, and transfer it to a nitrogen glove box for standby; spin-coat the photoactive solution on the HTL at a speed of 2500 rpm and anneal at 80 °C for 10 min. Subsequently, at a pressure lower than 6×10 -4Under a vacuum condition of Pa, C60 with a thickness of 35 nm and Al with a thickness of 150 nm are sequentially deposited through a patterned mask, and the effective area of the device is 0.35 cm 2 . Set the bending diameter of the device between 25 mm and 10 mm, and its bending parameters are as Figure 1 shown.

[0042] Example 2

[0043] Prepare a device structure of PET / ITO / PEDOT:PSS / C 100 H 116 N6O4S5 / C60 / Al. Place the PET / ITO substrate in an oxygen plasma cleaner for 10 min of plasma treatment on the surface; then spin-coat the PEDOT:PSS solution filtered through a nylon filter membrane on the ITO substrate at a speed of 3000 rpm, and obtain a hole transport layer thin film (HTL) by thermal annealing at 150 °C for 10 min, and transfer it to a nitrogen glove box for standby; spin-coat the photoactive solution on the HTL at a speed of 2500 rpm and anneal at 80 °C for 10 min. Subsequently, under a vacuum condition of less than 6×10 -4 Pa, C60 with a thickness of 35 nm and Al with a thickness of 150 nm are sequentially deposited through a patterned mask, and the effective area of the device is 0.35 cm 2 . Estimate the total noise with shot noise to evaluate the specific detectivity of the device. Its peak response at 1050 nm in the near-infrared region is 7.31×10 12 Jones, and the specific detectivity values within the response range generally exceed 10 12 Jones, enabling the device to have sensitive detection performance in the near-infrared region, which has exceeded the detection limit (1.1 μm) of commercially available silicon detectors, as Figure 2 shown.

[0044] Example 3

[0045] Prepare a device structure of PET / ITO / PEDOT:PSS / C 100 H 116 N6O4S5 / C60 / Al. Place the PET / ITO substrate in an oxygen plasma cleaner for 10 min of plasma treatment on the surface; then spin-coat the PEDOT:PSS solution filtered through a nylon filter membrane on the ITO substrate at a speed of 3000 rpm, and obtain a hole transport layer thin film (HTL) by thermal annealing at 150 °C for 10 min, and transfer it to a nitrogen glove box for standby; spin-coat the photoactive solution on the HTL at a speed of 2500 rpm and anneal at 80 °C for 10 min. Subsequently, under a vacuum condition of less than 6×10 -4Under a vacuum condition of Pa, C60 with a thickness of 35 nm and Al with a thickness of 150 nm are sequentially deposited through a patterned mask, and the effective area of the device is 0.35 cm 2 。The responsivity of the device in the near-infrared light region is detected. It can be seen that the peak responsivity of the prepared flexible photodetector in the near-infrared light region is 34.49 mA W -1 @1050 nm. The bending diameter is set to 15 mm. After bending 100 times, the peak responsivity drops to 34.05 mA W -1 @1050 nm. Comparing the responsivity of the flexible device before and after 100 bends with a bending diameter d ranging from 25 mm to 10 mm, the average responsivity only drops by about 2%, as Figure 3 shown. This demonstrates the good mechanical stability of the flexible device.

[0046] Example 4

[0047] The device structure is prepared as PET / ITO / PEDOT:PSS / C 100 H 116 N6O4S5 / C60 / Al. The PET / ITO substrate is placed in an oxygen plasma cleaner for 10 min of plasma treatment on the surface; subsequently, the PEDOT:PSS solution filtered through a nylon filter membrane is spin-coated on the ITO substrate at a speed of 3000 rpm and thermally annealed at 150 °C for 10 min to obtain a hole transport layer film (HTL), which is transferred to a nitrogen glove box for standby; the photoactive solution is spin-coated on the HTL at a speed of 2500 rpm and annealed at 80 °C for 10 min. Subsequently, under a vacuum condition of less than 6×10 -4 Pa, C60 with a thickness of 35 nm and Al with a thickness of 150 nm are sequentially deposited through a patterned mask, and the effective area of the device is 0.35 cm 2 。The dark current density of the device is measured. As Figure 4 shown, thanks to the sequential deposition process of PHJ-OPDs to form the donor and acceptor layers, an ordered phase separation structure is obtained in the vertical direction, enabling the device to obtain stable interface and optoelectronic properties. The donor phase and acceptor phase are in contact with the hole transport layer and electron transport layer respectively to form an interface, resulting in a high injection barrier for the device, which can effectively reduce the leakage current and thus suppress the dark current. In addition, the single-molecule film is easier to achieve low trap states and high morphological stability compared to the mixed-phase film, hindering the bimolecular charge recombination and suppressing the energy disorder, enabling the carriers to transport in the pure donor and acceptor phases. The dark current density of the device at zero bias under different bending diameters is still at the level of 10 -10 Acm -2 magnitude, proving that the device has good flexibility.

[0048] Example 5

[0049] The device structure is prepared as PET / ITO / PEDOT:PSS / C 100 H 116 N6O4S5 / C60 / Al. Place the PET / ITO substrate in an oxygen plasma cleaner for 10 min of plasma treatment on the surface. Subsequently, spin-coat the PEDOT:PSS solution filtered through a nylon filter membrane onto the ITO substrate at a speed of 3000 rpm, and perform thermal annealing at 150 °C for 10 min to obtain a hole transport layer film (HTL), and transfer it to a nitrogen glove box for standby. Spin-coat the photoactive solution onto the HTL at a speed of 2500 rpm and anneal at 80 °C for 10 min. Subsequently, under a vacuum condition of less than 6×10 -4 Pa, deposit C60 with a thickness of 35 nm and Al with a thickness of 150 nm in sequence through a patterned mask. The effective area of the device is 0.35 cm 2 . Since near-infrared light has a stronger penetration ability in human tissues, respectively test the response signals of the flexible photodetector to 980 nm and 1064 nm near-infrared light transmitted through the fingertips, as Figure 5 shown. The PPG waveform diagram shows a pulse signal synchronized with the heartbeat, and each cycle corresponds to one heartbeat. Extract the heart rate information of the measured person from the waveform signal. The flexible device measures a heart rate of 71 min -1 under 980 nm light illumination and a heart rate of 73 min -1 under 1064 nm light illumination. The results are consistent with the actual situation, indicating that the flexible device has application potential in the field of health monitoring.

[0050] Therefore, the present invention adopts a preparation process of a flexible planar heterojunction type near-infrared photodetector with the above structure. A near-infrared photodetector that can be used for human heart rate monitoring is prepared through a simple and efficient planar heterojunction preparation process, and excellent device stability is obtained. A streamlined and efficient planar heterojunction type diode structure is adopted, which can effectively reduce the complexity of device preparation, save preparation costs and time. The prepared near-infrared photodetector has a light response range covering the visible light-near-infrared region, and the detectable wavelength range exceeds 1.3 microns. Applying the photoactive material to the flexible OPD device can achieve a specific detectivity of more than 10 12 Jones in the near-infrared >1.1 μm region, which has broken through the detection limit of commercially available silicon photodetectors. The dark current density is on the order of 10 -10 A cm -2 , and the human pulse frequency can be accurately measured under light irradiation of different wavelengths.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions of the present invention or make equivalent replacements, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A preparation process of a flexible planar heterojunction type near-infrared photodetector, characterized in that, The structure of the detector is PET / ITO / PEDOT:PSS / photoactive material layer / C60 / Al, and its preparation process specifically includes the following steps: a) Place the PET / ITO substrate in an oxygen plasma cleaner for plasma treatment of the surface; b) Subsequently, spin-coat the PEDOT:PSS solution filtered through a nylon filter membrane on the substrate, anneal to obtain a hole transport layer thin film, and transfer it to a nitrogen glove box for standby; c) Spin-coat the photoactive material solution and anneal it under a nitrogen atmosphere; d) Under vacuum conditions, deposit different thicknesses of C60 and Al in sequence through a patterned mask to form an effective detection area.

2. The preparation process of a flexible planar heterojunction type near-infrared photodetector according to claim 1, characterized in that, The photoactive material layer is a compound represented by the following general formula: C 96+x H 110+y N m O4S n , where x is 0 - 10, y is 0 - 6, m is 4 or 6, and n is 5 or 7.

3. The preparation process of a flexible planar heterojunction type near-infrared photodetector according to claim 1, characterized in that, In step a), the power of the oxygen plasma treatment is 100 - 300 W, and the treatment time is 10 minutes.

4. The preparation process of a flexible planar heterojunction type near-infrared photodetector according to claim 1, characterized in that, In step b), the hole transport layer thin film has a thickness of 30 - 50 nm. Spin-coat the PEDOT:PSS solution at a speed of 3000 rpm and anneal it at 150 °C for 10 minutes to obtain the hole transport layer thin film.

5. The preparation process of a flexible planar heterojunction type near-infrared photodetector according to claim 1, characterized in that, In step c), the photoactive material layer is prepared by spin-coating the solution at a concentration of 4 - 20 mg / mL at a speed of 2500 rpm and annealing it at 80 °C for 10 minutes.

6. The preparation process of a flexible planar heterojunction type near-infrared photodetector according to claim 1, characterized in that The thickness of the C60 layer described in step d) is 20 to 50 nm, and the thickness of the Al layer is 100 to 200 nm. Both are prepared by a vacuum evaporation process with a vacuum degree ≤ 6×10 -4 Pa.

7. The preparation process of a flexible planar heterojunction type near-infrared photodetector according to claim 1, characterized in that, The effective area of the detector is 0.35 cm 2 .

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