Circularly polarized light detector and preparation method thereof

Abstract

The invention discloses a circularly polarized light detector and a preparation method thereof, and belongs to the technical field of photoelectric detectors, and the circularly polarized light detector sequentially comprises a substrate, a gate electrode, a conjugated polymer layer, a chiral supramolecular layer, a source electrode and a drain electrode from bottom to top, so that the integration level can be greatly improved, and the overall size can be reduced to below 10cm. The device is suitable for application fields such as miniature endoscopes and wearable sensors with strict requirements on device sizes, the integration bottleneck caused by traditional optical element combination is avoided, the chiral supramolecular layer has an excellent coupling effect on circularly polarized light, left-handed circularly polarized light and right-handed circularly polarized light can be accurately distinguished, and the detection accuracy is improved. The asymmetric factor is obviously higher than that of an organic circularly polarized light detector based on traditional chiral small molecules or polymers.

Description

Technical Field

[0001] This invention relates to a circularly polarized light detector and its fabrication method, belonging to the field of photoelectric detector technology. Background Technology

[0002] Due to its helical propagation characteristics, circularly polarized light has become a key information carrier in fields such as biomedicine, quantum communication, and remote sensing. In biomedicine, the chiral phospholipid molecules in cancer cell membranes produce weak circularly polarized signal differences, requiring detectors with high asymmetry factors for early diagnosis. In quantum communication, circularly polarized states serve as carriers of qubits, requiring detectors with sub-second rapid response capabilities to meet the demands of high-speed signal processing. In remote sensing, the polarization reflectance spectral analysis of surface vegetation and atmospheric aerosols requires detectors to maintain long-term stability in the 400-1000 nm wavelength range.

[0003] However, traditional circular polarization detection systems rely on a combination architecture of polarizers, quarter-wave plates, and silicon-based detectors, which suffers from drawbacks such as a contradiction between size and integration, high cost and easy loss, and low polarization resolution, making it difficult to meet the needs of practical applications. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a circularly polarized light detector and its fabrication method. By combining the advantages of both chiral supramolecular layers and conjugated polymer layers in a heterojunction, it overcomes the problems of large size, low integration, low polarization resolution of traditional circularly polarized light detectors, as well as the low field-effect mobility and slow response of organic circularly polarized light detectors.

[0005] The technical solution adopted by this invention to solve its technical problem is: A circularly polarized light detector, from bottom to top, comprises a substrate, a gate electrode, a conjugated polymer layer, a chiral supramolecular layer, a source electrode, and a drain electrode, wherein: The conjugated polymer layer is a p-type organic semiconductor thin film with a thickness of 50-200 nm and a field-effect mobility ≥0.5 cm² / (V·s); The chiral supramolecular layer is a supramolecular co-assembly of chiral and achiral monomers, with a molar ratio of chiral to achiral monomers of 1:10 to 1:50. The thickness of the chiral supramolecular layer is 80-200 nm, and its circular polarization emission asymmetry factor for circularly polarized light at a wavelength of 532 nm is ≥0.15.

[0006] Preferably, the source electrode and drain electrode have a thickness of 70-90 nm, a spacing of 50 μm ± 5 μm, and a contact resistance of ≤ 1 kΩ.

[0007] Preferably, the substrate comprises a monocrystalline silicon wafer and a SiO2 insulating layer grown on its surface by thermal oxidation, wherein the resistivity of the monocrystalline silicon wafer is 1-10 Ω·cm and the thickness of the SiO2 insulating layer is 300 nm ± 5 nm; the gate electrode body is a monocrystalline silicon wafer and its lead-out terminal is a Cr / Au composite electrode.

[0008] Preferably, the material of the conjugated polymer layer is selected from poly(3-hexylthiophene) (P3HT), a polymer based on diketopyrrolopyrrole and thiophenothiophene (DPP-TT), or a polymer based on indenedithiophenothiophene and benzothiadiazole (IDTT-BT); wherein the number average molecular weight of P3HT is 5 × 10⁻⁶. 4 Up to 1×10 5 The region regularity is ≥98%; the number-average molecular weight of the DPP-TT is 8×10⁻⁶. 4 The number-average molecular weight of the IDTT-BT is 1.2 × 10⁻⁶. 5 .

[0009] Preferably, in the chiral supramolecular layer, the chiral monomer is (S)-2 or (R)-2, the achiral monomer is a compound containing a fluorene unit and a carboxyl group, and the molar ratio of the chiral monomer to the achiral monomer is 1:30.

[0010] Preferably, the chiral supramolecular layer is prepared by a mixed solvent of chlorobenzene and toluene, wherein the volume ratio of chlorobenzene to toluene is 7:3, the solvent purity is ≥99.8%, and the water content is ≤10ppm.

[0011] A method for fabricating a circularly polarized optical detector includes the following steps: S1: Provide and pre-process the substrate and gate electrode; S2: Prepare a conjugated polymer layer on the substrate; S3: Prepare a chiral supramolecular layer on the conjugated polymer layer; S4: Prepare source and drain electrodes on the chiral supramolecular layer; S5: Package the device.

[0012] Preferably, step S2 includes: The conjugated polymer powder was vacuum dried at 80°C and 10Pa for 12 hours. The dried conjugated polymer was dissolved in chlorobenzene solvent to prepare a solution with a concentration of 5-15 mg / mL. After stirring, sonicating and filtering, the solution was then spin-coated to form a film. The spin-coated film is then annealed at a temperature of 80-150℃ for 20-30 minutes. The parameters for the spin-coating film formation are as follows: First, spin coat at 500 rpm for 5 seconds to spread the solution, then spin coat at 1000-5000 rpm for 30 seconds to control the thickness. The spin coat speed for P3HT is 3000 rpm, for DPP-TT it is 4000 rpm, and for IDTT-BT it is 3500 rpm.

[0013] Preferably, step S3 includes: Chiral and achiral monomers were weighed at a molar ratio of 1:10 to 1:50, dissolved in a chlorobenzene / toluene mixed solvent, and co-assembled by stirring at 50°C for 4 hours. The co-assembled solution was deposited into a film by spin coating at a speed of 800-1500 rpm. The spin-coated film was annealed at 80°C for 2 hours.

[0014] Preferably, step S4 includes: Electrode patterns are defined using mask alignment techniques to ensure that the alignment deviation between the electrodes and the chiral supramolecular layer is ≤5μm. Vacuum degree ≤ 1×10 -5 Metal electrodes were deposited at a rate of 0.1-0.3 nm / s under Pa conditions.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: By introducing a heterojunction composed of a chiral supramolecular layer and a conjugated polymer layer, high-precision differentiation between left-handed and right-handed circularly polarized light is achieved, the asymmetry factor is significantly improved, and the problem of low polarization discrimination of traditional detectors is solved. The device has a highly integrated structure and a significantly reduced overall size, making it suitable for applications with stringent space requirements, such as miniature endoscopes and wearable devices. By combining the high selectivity of chiral supramolecular molecules with the high mobility of conjugated polymers, the detector not only possesses excellent circular polarization recognition capability, but also good electrical performance and fast response speed, resulting in superior overall performance. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of a partial structure of the device of the present invention; Figure 2 This is a structural diagram of the non-chiral monomer of the present invention; Figure 3 This is a structural diagram of the chiral monomer (S)-2 in this invention; Figure 4 This is a structural diagram of the chiral monomer (R)-2 in this invention; Figure 5 This is a diagram showing the drain-source current-gate-source voltage curves of the present invention under dark state, left-hand circularly polarized light, and right-hand circularly polarized light illumination. Figure 6 This is a drain-source current-time curve of the present invention under circularly polarized light irradiation.

[0018] In the figure: 1. Substrate; 2. Gate electrode; 3. Conjugated polymer layer; 4. Chiral supramolecular layer; 5. Source electrode; 6. Drain electrode. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1 This embodiment provides a circularly polarized light detector, the structure of which is as follows: Figure 1 As shown, from bottom to top, it includes a substrate 1, a gate electrode 2, a conjugated polymer layer 3, a chiral supramolecular layer 4, a source electrode 5, and a drain electrode 6.

[0021] Fabrication of substrate 1 and gate electrode 2: A single-crystal silicon wafer with a crystal orientation of (100) and a resistivity of 5 Ω·cm was selected as the conductive part of substrate 1. It was placed in a thermal oxidation furnace and a 300 nm thick silicon dioxide (SiO2) layer was grown at 1100 °C in an oxygen atmosphere as an insulating layer. The main body of the gate electrode 2 is the single-crystal silicon wafer itself. At the edge of the silicon wafer, a 10 nm thick layer of chromium (Cr) and a 40 nm thick layer of gold (Au) were sequentially deposited using electron beam evaporation to form a Cr / Au composite lead-out electrode with a contact resistance ≤50 Ω.

[0022] Preparation of conjugated polymer layer 3: Selected regions with regularity ≥98% and number-average molecular weight of approximately 8×10⁻⁶ 4Poly(3-hexylthiophene) (P3HT) was used as a p-type organic semiconductor material. First, P3HT powder was vacuum dried at 80℃ and 10 Pa for 12 hours to remove moisture. Then, the dried P3HT was dissolved in chlorobenzene to prepare a solution with a concentration of 10 mg / mL, and stirred in an oil bath at 60℃ for 2 hours until completely dissolved. After ultrasonic treatment and filtration through a 0.2 μm polytetrafluoroethylene (PTFE) membrane, the solution was spin-coated onto a pretreated SiO2 / Si substrate 1. The spin-coating parameters were: first, spin-coating at 500 rpm for 5 seconds to spread the solution, then spin-coating at 3000 rpm for 30 seconds. The spin-coated film was immediately transferred to a heating stage and annealed at 120℃ under a nitrogen atmosphere for 30 minutes. Finally, a P3HT conjugated polymer layer 3 with a thickness of approximately 80 nm, a smooth surface, and good crystallinity was obtained, with a field-effect mobility ≥0.5 cm² / (V·s).

[0023] Preparation of chiral supramolecular layer 4: In this embodiment, the chiral supramolecular layer 4 is formed by supramolecular co-assembly of chiral monomer (S)-2 and achiral monomer, wherein the structural formula of the achiral monomer is shown in […]. Figure 2 The structural formula of the chiral monomer (S)-2 is shown in [reference needed]. Figure 3 Two monomers were precisely weighed at a molar ratio of 1:30. The weighed monomers were dissolved in a mixed solvent of chlorobenzene and toluene, and the mixture was magnetically stirred at 50°C for 4 hours to allow for thorough supramolecular co-assembly, forming a homogeneous and stable solution. This co-assembled solution was spin-coated onto the aforementioned P3HT conjugated polymer layer 3 at a spin speed of 1500 rpm for 30 seconds. Subsequently, the film was annealed at 80°C for 2 hours to remove residual solvent and stabilize the supramolecular structure, ultimately forming a chiral supramolecular layer 4 with a thickness of approximately 80 nm. This layer exhibits a circular polarization emission asymmetry factor ≥0.15 for circularly polarized light at a wavelength of 532 nm.

[0024] Fabrication of source electrode 5 and drain electrode 6: Using a high-precision metal mask, it was precisely aligned with the device substrate having completed the chiral supramolecular layer 4, ensuring that the alignment deviation between the electrode pattern and the functional layer was ≤5μm. The substrate was then placed in a high-vacuum evaporation chamber at a vacuum level ≤1×10⁻⁶. -5 Under the condition of Pa, gold (Au) was deposited by vapor deposition at a rate of 0.2 nm / s. After the vapor deposition was completed, a pair of source electrodes 5 and drain electrodes 6 with a thickness of 80 nm and a spacing of 50 μm were obtained, with a contact resistance ≤1 kΩ.

[0025] The performance of the circularly polarized light detector prepared in this embodiment was tested. The output characteristics of the device were measured under illumination with circularly polarized light at a wavelength of 532 nm and a power density of 10 mW / cm². Figure 5As shown, the drain-source current (IDS) generated under left-hand circularly polarized light (L-CPL) illumination is significantly higher than that under right-hand circularly polarized light (R-CPL) illumination, while the dark-state current is extremely low, indicating that the device possesses excellent polarization resolution and on / off ratio. The asymmetry factor calculated from the photocurrent data reaches 0.18. The calculated field-effect mobility of the device is approximately 0.62 cm² / (V·s), and the response time is approximately 0.42 seconds. These performance indicators are significantly superior to detectors relying on traditional optical element combinations and also solve the problem of poor carrier transport performance in purely chiral organic semiconductors.

[0026] like Figure 6 As shown, when the laser is turned on, the photocurrent of the device rapidly rises to its peak value within approximately 0.42 seconds; when the laser is turned off, the photocurrent recovers to the dark state level within approximately 0.35 seconds. This rapid response characteristic demonstrates that the detector of this invention not only has high polarization sensitivity but also excellent dynamic detection capabilities, meeting the needs of applications such as real-time monitoring and high-speed communication.

[0027] Comparative Example 1 The fabrication of the blended circularly polarized light detector follows the same steps as in Example 1, except for the preparation method of the chiral recognition layer. Chiral monomer (S)-2 and P3HT are co-dissolved in chlorobenzene at a mass ratio of 1:20, spin-coated into a film, and then annealed at 100°C for 10 minutes to form the blended active layer.

[0028] Example 2 This embodiment aims to illustrate the impact of using different conjugated polymer materials and optimizing the ratio of chiral components on the overall performance of the detector.

[0029] Substrate 1 and gate electrode 2: The fabrication process is the same as in Example 1.

[0030] Conjugated polymer layer 3: A polymer based on diketopyrrolopyrrole and thiophenothiophene (DPP-TT) was selected and prepared into a 10 mg / mL chlorobenzene solution. The solution was spin-coated onto substrate 1 at 4000 rpm and then annealed at 150 °C for 20 minutes to form a film with a thickness of about 100 nm.

[0031] Chiral supramolecular layer 4: To investigate the optimal ratio, co-assembled solutions of chiral monomer (R)-2 and achiral monomer at molar ratios of 1:20, 1:30, and 1:40 were prepared, respectively. The structural formula of (R)-2 is shown in [reference needed]. Figure 4 As shown, the three solutions were spin-coated (1200 rpm) onto the DPP-TT layer and annealed at 80 °C for 2 hours to form a chiral supramolecular layer 4 with a thickness of about 120 nm.

[0032] Source electrode 5 and drain electrode 6: The preparation process is the same as in Example 1.

[0033] Performance Comparison and Analysis: Molar ratio 1:20: chiral recognition ability is the strongest, and the measured asymmetry factor is about 0.19. However, the higher chiral component may slightly affect the interfacial charge transport, and the field-effect mobility is about 0.48 cm² / (V·s).

[0034] A molar ratio of 1:30 achieves the best balance between polarization recognition and electrical performance, with an asymmetry factor of approximately 0.18, field-effect mobility increased to 0.55 cm² / (V·s), and the best film uniformity.

[0035] Molar ratio 1:40: Chiral recognition ability is slightly reduced, but charge transport is smoother.

[0036] This embodiment demonstrates that a molar ratio of 1:30 within the range of 1:10 to 1:50 can achieve synergistic optimization of high performance. This differs from the prior art's approach of attempting to balance performance through complex heterostructures. This invention can achieve this through simple supramolecular co-assembly ratio control.

[0037] Example 3: This embodiment emphasizes the critical role of the selectivity of conjugated polymer materials and the purity of the solvent used to prepare the chiral supramolecular layer in the stability of device performance.

[0038] Substrate 1 and gate electrode 2: The fabrication process is the same as in Example 1.

[0039] Conjugated polymer layer 3: A polymer based on indene dithiophene and benzothiadiazole (IDTT-BT) was selected. A solution with a concentration of 12 mg / mL was prepared using chlorobenzene. After filtration, the solution was spin-coated at 3500 rpm and annealed at 140°C for 25 minutes to form a film with a thickness of about 150 nm.

[0040] Chiral supramolecular layer 4: Solvent quality was strictly controlled in this embodiment. Analytical grade chlorobenzene and toluene with a purity ≥99.8% and a water content ≤10ppm were used and mixed strictly at a volume ratio of 7:3. (S)-2 and the achiral monomer were weighed at a molar ratio of 1:30 and dissolved in the above high-purity mixed solvent. The mixture was stirred at 50°C for 4 hours for assembly. Subsequently, it was spin-coated onto the IDTT-BT layer at 1000 rpm and annealed at 80°C for 2 hours to form a high-quality chiral supramolecular layer 4 with a thickness of approximately 180 nm.

[0041] Source electrode 5 and drain electrode 6: The preparation process is the same as in Example 1.

[0042] Performance and Stability: Under 532 nm CPL irradiation, the obtained device exhibits an asymmetry factor of approximately 0.17 and a field-effect mobility of approximately 0.58 cm² / (V·s). Due to the wide absorption characteristics of IDTT-BT, the device demonstrates good polarization response in the visible light band. Comparative experiments revealed that using common solvents with high water content significantly reduces the film quality of the chiral supramolecular layer 4, resulting in pinholes and a decrease in the asymmetry factor exceeding 30%. Furthermore, the device's performance degradation accelerates under humid and hot conditions. This embodiment demonstrates that the defined solvent purity parameters are crucial for ensuring the reproducibility and long-term stability of the device performance.

[0043] Key performance parameters of Example 1 and Comparative Example 1 are compared, as shown in Table 1 below:

[0044] The effect of solvent purity on the long-term stability of the device is shown in Table 2 below:

[0045] Analysis of the data in Table 1 clearly shows that Example 1 significantly outperforms Comparative Example 1 in all key indicators, including mobility, g-factor, and response speed. This result confirms that the functional decoupling design effectively resolves the inherent contradiction between poor carrier transport in chiral materials and weak chiral recognition in conjugated polymers, a conventional optimization not expected by those skilled in the art.

[0046] In Example 1, a molar ratio of 1:30 represents the optimal window for supramolecular ordered assembly and charge transport equilibrium. In Table 2, a solvent purity of ≥99.99% is a necessary condition to ensure the long-term stability of the device. Trace amounts of moisture can lead to supramolecular structure damage and interface defects.

[0047] Example 2 demonstrates that the technical solution of the present invention is applicable to a variety of high-mobility conjugated polymer systems (P3HT, DPP-TT, IDTT-BT), and can achieve synergistic optimization of mobility ≥0.5 cm² / (V·s) and g ≥0.15, reflecting the scalability of the solution.

[0048] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A circularly polarized light detector, characterized in that, From bottom to top, the structure includes a substrate (1), a gate electrode (2), a conjugated polymer layer (3), a chiral supramolecular layer (4), a source electrode (5), and a drain electrode (6), wherein: The conjugated polymer layer (3) is a p-type organic semiconductor thin film with a thickness of 50-200 nm and a field effect mobility ≥0.5 cm² / (V·s); The chiral supramolecular layer (4) is a supramolecular co-assembly of chiral monomers and achiral monomers, wherein the molar ratio of chiral monomers to achiral monomers is 1:10 to 1:50, the thickness of the chiral supramolecular layer (4) is 80-200 nm, and its circular polarization emission asymmetry factor for circularly polarized light at a wavelength of 532 nm is ≥0.

15. In the chiral supramolecular layer (4), the chiral monomer is (S)-2 or (R)-2, the achiral monomer is a compound containing fluorene unit and carboxyl group, and the molar ratio of the chiral monomer to the achiral monomer is 1:

30. The material of the conjugated polymer layer (3) is selected from one of poly(3-hexylthiophene) (P3HT), a polymer based on diketopyrrolopyrrole and thiophenothiophene (DPP-TT), or a polymer based on indene dithiophenothiophene and benzothiadiazole (IDTT-BT); wherein the number average molecular weight of P3HT is 5 × 10⁻⁶. 4 Up to 1×10 5 The region regularity is ≥98%; the number-average molecular weight of the DPP-TT is 8×10⁻⁶. 4 The number-average molecular weight of the IDTT-BT is 1.2 × 10⁻⁶. 5 .

2. A circularly polarized light detector according to claim 1, characterized in that, The thickness of the source electrode (5) and the drain electrode (6) is 70-90nm, the spacing is 50μm±5μm, and the contact resistance is ≤1kΩ.

3. A circularly polarized light detector according to claim 1, characterized in that, The substrate (1) includes a single-crystal silicon wafer and a SiO2 insulating layer grown on its surface by thermal oxidation. The resistivity of the single-crystal silicon wafer is 1-10 Ω·cm, and the thickness of the SiO2 insulating layer is 300nm±5nm. The gate electrode (2) is mainly a single-crystal silicon wafer, and its lead-out end is a Cr / Au composite electrode.

4. A circularly polarized light detector according to claim 1, characterized in that, The chiral supramolecular layer (4) is prepared by a mixed solvent of chlorobenzene and toluene, wherein the volume ratio of chlorobenzene to toluene is 7:3, the solvent purity is ≥99.8%, and the water content is ≤10ppm.

5. A method for preparing a circularly polarized light detector as described in any one of claims 1-4, characterized in that, Includes the following steps: S1: Provide and pre-treat the substrate (1) and the gate electrode (2); S2: Prepare a conjugated polymer layer (3) on the substrate (1); S3: Prepare a chiral supramolecular layer (4) on the conjugated polymer layer (3); S4: Prepare source electrode (5) and drain electrode (6) on the chiral supramolecular layer (4); S5: Package the device.

6. The method for fabricating a circularly polarized optical detector according to claim 5, characterized in that, Step S2 includes: The conjugated polymer powder was vacuum dried at 80°C and 10Pa for 12 hours. The dried conjugated polymer was dissolved in chlorobenzene solvent to prepare a solution with a concentration of 5-15 mg / mL. After stirring, sonicating and filtering, the solution was then spin-coated to form a film. The spin-coated film is then annealed at a temperature of 80-150℃ for 20-30 minutes. The parameters for the spin-coating film formation are as follows: First, spin coat at 500 rpm for 5 seconds to spread the solution, then spin coat at 1000-5000 rpm for 30 seconds to control the thickness. The spin coat speed for P3HT is 3000 rpm, for DPP-TT it is 4000 rpm, and for IDTT-BT it is 3500 rpm.

7. The method for fabricating a circularly polarized optical detector according to claim 5, characterized in that, Step S3 includes: Chiral and achiral monomers were weighed at a molar ratio of 1:10 to 1:50, dissolved in a chlorobenzene / toluene mixed solvent, and co-assembled by stirring at 50°C for 4 hours. The co-assembled solution was deposited into a film by spin coating at a speed of 800-1500 rpm. The spin-coated film was annealed at 80°C for 2 hours.

8. A method for fabricating a circularly polarized light detector according to claim 5, characterized in that, Step S4 includes: Electrode patterns are defined using mask alignment techniques to ensure that the alignment deviation between the electrodes and the chiral supramolecular layer is ≤5μm. Vacuum degree ≤ 1×10 -5 Metal electrodes were deposited at a rate of 0.1-0.3 nm / s under Pa conditions.

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