Organic photoelectric detector for regulating and controlling molecular accumulation based on anti-solvent method and preparation method of organic photoelectric detector

Abstract

The organic photoelectric detector comprises a conductive substrate, an electron transport layer, an active layer, a hole transport layer and a metal electrode from top to bottom, an active layer film is prepared by using the anti-solvent method, and an anti-solvent is n-hexane. The conductive substrate is ITO conductive glass, FTO conductive glass, AZO conductive glass or TCO conductive glass. According to the organic photoelectric detector for regulating and controlling molecule accumulation based on the anti-solvent method and the preparation method of the organic photoelectric detector, the film forming dynamics of the bulk heterojunction active layer is influenced, donor and acceptor molecules are induced to be tightly and orderly accumulated, the dark current density is reduced, the external quantum efficiency and the specific detection rate are improved, and the specific detection rate of the device is larger than 1 * 10 < 14 > jones between 335 nm and 655 nm.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic device technology, specifically to an organic photodetector and its preparation method that utilizes an antisolvent method to directly control the molecular stacking of the active layer. Background Technology

[0002] Organic photodetectors (OPDs) have shown great application potential in fields such as image sensing, biomedical detection, and environmental monitoring due to their advantages such as light weight, good flexibility, solution-processability, and ease of fabrication of large-area devices. The core of an OPD is a bulk heterojunction active layer formed by blending donor and acceptor materials. The molecular packing morphology, phase separation scale, and crystallinity of the internal materials directly determine the key performance parameters of the device, such as external quantum efficiency, dark current, and detectivity.

[0003] Currently, common methods for optimizing the morphology of the OPD active layer include solvent annealing, thermal annealing, and the use of high-boiling-point solvent additives. However, these methods often suffer from problems such as complex processes, poor reproducibility, or insufficient precision in controlling the final morphology. For example, while the use of solvent additives is effective, their residues may affect the long-term stability of the device; thermal annealing may lead to excessive phase separation, which is detrimental to charge generation and separation.

[0004] Therefore, there is an urgent need in this field to develop a new method that is simple to process, highly controllable, and can effectively optimize the molecular stacking and nanoscale phase separation of the active layer, enhance the quality of the active layer film, and thus simultaneously improve the external quantum efficiency of OPD and suppress dark current. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention discloses an organic photodetector based on the antisolvent method for regulating the molecular stacking of the active layer and its preparation method. In this invention, the antisolvent method introduces n-hexane as an antisolvent into the heterojunction active layer solution of the organic photodetector bulk, directly inducing the orderly stacking of donor and acceptor molecules, thereby significantly improving the detection performance of the device.

[0006] The technical solution for achieving the objective of this invention is as follows: A method for fabricating an organic photodetector based on antisolvent-mediated molecular stacking, wherein the organic photodetector structure comprises, from top to bottom, a conductive substrate, an electron transport layer, an active thin film, a hole transport layer, and a metal electrode, wherein the active thin film is prepared using an antisolvent-mediated method.

[0007] Furthermore, the transparent conductive substrate can be ITO conductive glass, or it can be FTO, AZO, or TCO.

[0008] Furthermore, the electron transport layer can be ZnO or PNDIT-F3N.

[0009] Furthermore, the organic material of the bulk heterojunction active layer can be P3HT:PCBM, PM6:Y6, or PTB7-Th:COTIC-4F.

[0010] Furthermore, the hole transport layer can be MoO3 or PEDOT:PSS.

[0011] Furthermore, the metal electrode can be gold or silver.

[0012] Furthermore, the active layer solution containing hexane as an antisolvent has a volume ratio of hexane to the active layer solution of 1:1.

[0013] Furthermore, the conductive substrate is ITO conductive glass, the film thickness of which is 135 nm, the transmittance is ≥86%, and the sheet resistance is ≤15. Furthermore, the electron transport layer is ZnO. The concentration of ZnO is 0.1-0.2 g / ml. Furthermore, the organic material of the active layer film is P3HT:PC. 70 BM. The P3HT and PC 70 The concentration of BM is 40 mg / mL.

[0014] Moreover, the hole transport layer is MoO3 with a thickness of 5 nm.

[0015] The beneficial effects of this invention are as follows: This invention relates to an organic photodetector based on antisolvent-induced molecular stacking and its fabrication method. This method influences the film-forming dynamics of the bulk heterojunction active layer, inducing the tight and orderly stacking of donor and acceptor molecules, reducing dark current density, and improving external quantum efficiency and specific detectivity. The specific detectivity of the device exceeds 1×10¹⁴ Jones in the 335nm–655nm range. Furthermore, the low price of n-hexane provides a reference for the large-area industrial fabrication of high-performance organic photodetectors. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of an organic photodetector based on antisolvent method for controlling molecular stacking according to an embodiment of the present invention.

[0017] Figure 2 This is an AFM characterization diagram of the active layer in Example 1.

[0018] Figure 3 This is an AFM characterization diagram of the comparative active layer.

[0019] Figure 4 The graph shows the relationship between dark current density and voltage for the organic photodetector in Example 1 and the comparative organic photodetector.

[0020] Figure 5 The diagram shows the external quantum efficiency (EQE) of the organic photodetector in Example 1 and the comparative organic photodetector.

[0021] Figure 6 The diagram shows the responsivity of the organic photodetector in Example 1 and the comparative organic photodetector.

[0022] Figure 7 The detectivity diagrams are for the organic photodetector of Example 1 and the comparative organic photodetector. Detailed Implementation

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] The following examples further illustrate the specific implementation of the present invention, but the implementation and protection of the present invention are not limited thereto. It should be noted that any processes not specifically described below are those that can be implemented or understood by those skilled in the art by referring to existing technology. Reagents or instruments whose manufacturers are not specified are considered to be conventional products that can be purchased commercially.

[0025] This invention provides an organic photodetector based on antisolvent-based molecular packing modulation, the structure of which is as follows: Figure 1 As shown, from top to bottom, it includes an anode (conductive substrate), a hole transport layer, an active layer thin film, an electron transport layer, and a cathode (metal electrode).

[0026] Furthermore, the conductive substrate is ITO conductive glass, the film thickness of which is 135 nm, the transmittance is ≥86%, and the sheet resistance is ≤15. Furthermore, the electron transport layer is ZnO. The concentration of ZnO is 0.1-0.2 g / ml. Furthermore, the organic material of the active layer film is P3HT:PC. 70 BM. The P3HT and PC 70 The concentration of BM is 40 mg / mL.

[0027] Furthermore, the hole transport layer is MoO3 with a thickness of 5 nm.

[0028] Furthermore, the metal electrode is made of silver and has a thickness of 100 nm.

[0029] Example 1 The organic photodetector structure in this embodiment is ITO / ZnO / P3HT:PC. 61 BM / MoO3 / Ag.

[0030] The fabrication process of the above-mentioned organic photodetector device includes the following steps: S1. Clean the ITO conductive glass sequentially with detergent, deionized water, acetone, anhydrous ethanol, and isopropanol, each ultrasonically for 15-20 minutes. Before use, blow away any residual solvent on the substrate with nitrogen. The ITO conductive glass has a film thickness of 135nm, a light transmittance ≥86%, and a sheet resistance ≤15.

[0031] S2. Perform a 5-minute surface plasma treatment on the dried ITO conductive glass (the radio frequency power of the plasma treatment is 80W). This treatment method uses the strong oxidizing property of ozone generated under microwaves to clean residual organic matter on the ITO surface. At the same time, it can increase the oxygen vacancies on the ITO surface and improve the work function of the ITO surface.

[0032] S3. Prepare the zinc oxide precursor in the following ratio: 100 mg zinc acetate dihydrate, 1 mL 2-methoxyethanol and 28 μL ethanol gel. Stir and dissolve at room temperature for 10 hours. Filter before use. The ZnO concentration is 0.1-0.2 g / ml.

[0033] S4. The ZnO solution prepared in step S3 is statically rotated on the ITO surface after S2 treatment at a speed of 4000 rpm for 30 seconds, and then annealed at 200℃ for 30 minutes to form an electron transport layer, which is then transferred to the active layer spin-coated in the glove box.

[0034] S5. Processing of the active layer: The concentration of the active layer solution is 40 mg / mL, the solvent is chlorobenzene, and the donor (P3HT) and acceptor (PC) are used. 70 The mass ratio of BM is 1:1. The solution needs to be stirred at 60°C for at least 3 hours. After complete dissolution, add the same volume of n-hexane as chlorobenzene and stir at 60°C for 2 minutes. Prepare and use immediately. (The concentration of both the donor and acceptor is 40 mg / mL). For each spin coating, take 18 μL of the active layer solution, spin at 2000 rpm for 30 seconds. After spin coating, anneal on a hot plate at 120°C for 10 minutes.

[0035] S6. Deposit a hole transport layer on the surface of the above-mentioned active layer. Place the substrate with the spin-coated active layer onto a mask, and deposit a 5 mm thick layer of molybdenum oxide (MoO3) in all areas except the common electrode region. The deposition conditions are: vacuum chamber pressure less than 2 x 10⁻⁶. -4 The evaporation rate is less than 0.20 nm / s. After evaporation, the wafer is removed, and the active layer and electron transport layer in the common electrode area are scratched to expose the bottom ITO electrode.

[0036] S7. Anode silver (Ag) is deposited on the surface of the hole transport layer under vacuum pressure less than 2 x 10⁻⁶. -4 Evaporation begins at Pa, with a deposition thickness of 100 nm.

[0037] S8. After the above steps are completed, an organic photodetector based on the antisolvent method to control molecular packing is obtained. The effective area of ​​the finally fabricated device is 0.036 cm². 2 .

[0038] Comparative Example The comparative example follows the same steps as Example 1, except that the concentration of the active layer solution is 20 mg / mL and hexane is not introduced as an antisolvent. All other parameters are the same as in Example 1.

[0039] Figure 2 The image shows the AFM characterization of the active layer in Example 1, with a surface roughness Rq = 1.62 nm. Figure 3 The AFM characterization image of the comparative active layer shows a surface roughness Rq = 0.93 nm. This indicates that the addition of n-hexane as an antisolvent promotes moderate aggregation of donors and acceptors in the active layer film.

[0040] Table 1 Comparison of test data between Example 1 and comparative example.

[0041] Table 1 shows that the dark current density J in Example 1 d Compared to the comparative example of 1.16×10 -11 A / cm 2 Reduced to 2.01×10 -12 A / cm 2 The highest specific detectivity is 1.11 × 10⁻⁶. 14 Jones@510nm improved to 3.58×10 14 The result of jones@600nm indicates that the internal defects of the organic photodetector based on the antisolvent method to control molecular stacking are effectively suppressed, and the light absorption and conversion efficiency are improved.

[0042] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. An organic photodetector based on antisolvent-based molecular stacking modulation, characterized in that: From top to bottom, it includes a conductive substrate, an electron transport layer, an active layer, a hole transport layer, and a metal electrode. The active layer film is prepared using an anti-solvent method, wherein the anti-solvent is n-hexane.

2. The organic photodetector based on antisolvent-based molecular stacking control according to claim 1, characterized in that: The conductive substrate is ITO conductive glass, FTO conductive glass, AZO conductive glass or TCO conductive glass.

3. The organic photodetector based on antisolvent-based molecular stacking control according to claim 1, characterized in that: The electron transport layer can be ZnO or PNDIT-F3N.

4. The organic photodetector based on antisolvent-based molecular stacking control according to claim 1, characterized in that: The active layer is P3HT:PCBM, PM6:Y6, or PTB7-Th:COTIC-4F.

5. The organic photodetector based on antisolvent-based molecular stacking control according to claim 1, characterized in that: The hole transport layer can be MoO3 or PEDOT:PSS.

6. The organic photodetector based on antisolvent-based molecular stacking control according to claim 1, characterized in that: The metal electrode is made of gold or silver.

7. The process for preparing the organic photodetector based on antisolvent-controlled molecular stacking as described in claim 1, characterized in that: The steps are as follows: S1. Clean and dry the conductive substrate; S2. Perform surface plasma treatment on the dried conductive substrate; S3. Prepare an electron transport layer solution with a final concentration of 0.1 g / mL; S4. The electron transport layer solution prepared in step S3 is statically rotated on the surface of the conductive substrate treated in S2. S5. Preparation of active layer: The concentration of active layer solution is 20-40 mg / mL. After complete dissolution, add n-hexane and stir. Then spin-coate the active layer and anneal it after completion. S6. After annealing, deposit a hole transport layer on the surface of the active layer in S5. Place the substrate with the spin-coated active layer on a mask and deposit the hole transport layer.

8. The preparation process according to claim 7, characterized in that: The volume ratio of the n-hexane-containing solution to the active layer solution is 1:

1.

9. The preparation process according to claim 7, characterized in that: After adding n-hexane, stir at 50-70℃ for 1-5 minutes.

10. The preparation process according to claim 7, characterized in that: The ITO conductive glass has a film thickness of 135nm, a light transmittance of ≥86%, and a sheet resistance of ≤15.

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