Stacked controllably axially grown carbon quantum belts and two-dimensional thin films and their preparation and use

Abstract

The present application relates to the field of carbon nanomaterials, in particular to stack-controllable axial growth carbon quantum belt and two-dimensional film and preparation and application thereof. The present application takes 5,7,12,14-pentacene tetrone as a carbon source precursor, and axial growth carbon quantum belt and two-dimensional film which can be solution-processed and stack-controlled are obtained through formamide solvothermal method under concentrated sulfuric acid condition. The axial growth carbon quantum belt prepared by the present application can control the conjugated stacking mode between molecules through weak interaction force, form two-dimensional film with dense surface and good conductivity, and has wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of carbon nanomaterials, specifically to stacked and controllably grown axial carbon quantum bands and two-dimensional thin films, their preparation and applications. Background Technology

[0002] After decades of development, the power conversion efficiency (PCE) of solar cells (SCs) has increased dramatically from less than 0.1% to 20%. However, for currently reported active layer materials, including perovskite crystals and organic molecules, devices generally cannot maintain high performance during long-term operation, which seriously hinders their practical application. Therefore, there is an urgent need to develop a high-quality material to overcome this limitation. Carbon quantum dots (CQDs) have been widely used in optoelectronic fields, such as electroluminescent diodes, due to their high photothermal stability, tunable bandgap luminescence, good solution processability, low cost, and low toxicity. It is noteworthy that, according to the energy balance in the Shockley-Quieisser equation, a good light-emitting diode should also be a highly efficient SC, where efficient external luminescence is a necessary condition for low internal optical loss. For example, carbon dot-silver nanoparticle composites can serve as an interface layer to improve the device performance of polymer SCs, where the luminescence intensity of films containing silver nanoparticles is about 30% higher than that of films without silver nanoparticles. Furthermore, carbon dots can be incorporated into the device structure of perovskite SCs to improve long-term stability and reduce toxicity, which further confirms the great development potential of CQDs in SCs.

[0003] The charge movement process in SCs can be divided into several stages. First, photogenerated excitons are separated and dissociated into free charge carriers (such as holes and electrons) through diffusion. These carriers are then extracted and collected by the electrodes on both sides, ultimately converting light energy into electrical energy. However, CQDs as active layers still face a series of problems, mainly including the following: First, due to the unique quantum confinement effect of nanomaterials, quantum-sized CQDs experience severe energy level splitting, resulting in a narrow absorption spectrum and extremely low energy absorption efficiency in the visible light range (~400-800 nm). Second, considering the finite spt of CQDs... 2 The conjugated planar structure of CQDs tends to confine excitons to a single point, resulting in tight charge binding and hindering efficient electron-hole separation. Furthermore, CQDs typically exhibit irregular atomic arrangements and uncontrolled π-π aggregation, leading to highly delocalized electron clouds and undirected charge transfer. Therefore, overcoming the quantum size limitations and disordered π-aggregation of CQDs is crucial for achieving efficient electron-hole separation and directional exciton transport.

[0004] Generally, in transport networks composed of shorter molecules, electron transport is primarily hopping, while in networks composed of longer molecules, electron transport is more susceptible to band conduction, a key concern in organic charge transfer devices (SCs) designed based on D-π-A molecules. Therefore, designing strong electron-withdrawing functional groups on both sides of the carbon core and controlling the directional growth of the carbon core are beneficial for regulating the electron cloud arrangement in CQDs, thereby enabling the control of charge transfer direction. This not only controls the energy levels between orbitals but also effectively dissociates excitons to form holes and electrons. Furthermore, as charge diffuses to the molecular interface, specific structural stacking of the π-conjugated backbone, such as edge pairs or face pairs, holds promise for directional charge transport, thereby improving device performance. Therefore, fabricating CQDs that are solution-processable, exhibit good charge transport performance, high charge separation efficiency, and a wide absorption range is essential for developing high-efficiency SCs using high-quality thin films, but significant challenges remain. Summary of the Invention

[0005] This invention addresses the problems of narrow absorption range, poor solvent performance, poor film formation, weak charge transport capability, and mismatch between electron and hole mobility in currently reported CQDs. It proposes a stacked and controllable axially grown carbon quantum band and two-dimensional thin film, its preparation method, and its applications.

[0006] The purpose of this invention is to provide a stacked, controllable, axially grown carbon quantum ribbon.

[0007] Another object of the present invention is to provide a method for preparing the above-mentioned stacked and controllable axially grown carbon quantum bands.

[0008] Another object of the present invention is to provide a method for preparing a two-dimensional thin film of carbon quantum bands with controllable stacking and axial growth as described above.

[0009] Another object of the present invention is to provide an application of the above-described two-dimensional thin film of axially grown carbon quantum bands with controllable stacking.

[0010] The stacked, controllable, axially grown carbon quantum ribbons according to the present invention are prepared by a method comprising the following steps:

[0011] Using 5,7,12,14-pentaphenyltetraone as a carbon source precursor, the mixture was ultrasonically stirred to fully dissolve it in formamide. A small amount of concentrated sulfuric acid was added to the reaction system to promote the reaction of the precursor. The solution was then transferred to a beaker and a stainless steel high-pressure reactor lined with polytetrafluoroethylene. The reaction was carried out at 220 °C for 6 hours to obtain a solution of carbon quantum bands with controllable stacking and axial growth. Further, a solid carbon quantum band with controllable stacking and axial growth was obtained.

[0012] According to the present invention, the stacked and controllable axially grown carbon quantum ribbons are neutralized to pH = 7 with concentrated sulfuric acid, the supernatant is removed by centrifugation, deionized water is added for multiple washings, and then filtered to obtain a black solid powder. The sample is dried and purified by silica gel column to obtain the solid powder of the stacked and controllable axially grown carbon quantum ribbons.

[0013] According to the technical solution of the present invention, 5,7,12,14-pentaphenyltetraone is selected as the carbon source precursor. By controlling the different activities of the two reaction sites of 5,7,12,14-pentaphenyltetraone in the precursor, the solvothermal reaction conditions such as reaction time, reaction temperature, and the addition of catalyst are controlled to synthesize carbon quantum bands with controllable stacking and axial growth.

[0014] According to the technical solution of the present invention, the reaction solvent formamide is crucial for preparing carbon quantum bands with controllable stacking and axial growth. If the reaction solvent is replaced with other solvents such as ethanol, water, or ethyl acetate, while keeping other reaction conditions consistent, it is impossible to obtain carbon quantum bands with controllable stacking and axial growth.

[0015] According to the technical solution of the present invention, the acid plays a crucial role in regulating the reaction of the precursor and generating axially growing carbon quantum bands with controllable stacking. Without the addition of concentrated sulfuric acid, it is impossible to synthesize axially growing carbon quantum bands with controllable stacking by changing other reaction conditions such as temperature and time.

[0016] A solution of chlorobenzene containing axially grown carbon quantum bands with controlled stacking was dropped onto the surface of a highly oriented pyrolytic graphite substrate and placed at 10°C. -4 In a high vacuum atmosphere, the sample was heated at 80 °C for 15 minutes to form a film. The sample was then naturally cooled to room temperature, and the surface was rinsed with ethanol to obtain a two-dimensional thin film of axially grown carbon quantum bands with controllable stacking.

[0017] According to the technical solution of the present invention, a chlorobenzene solution of stacked and controllably grown axial carbon quantum ribbons is dropped onto the surface of a highly oriented pyrolytic graphite substrate. After the liquid is completely spread, the excess liquid is absorbed by degreased cotton to obtain a two-dimensional thin film of stacked and controllably grown axial carbon quantum ribbons.

[0018] According to the technical solution of the present invention, the surface of the highly oriented pyrolytic graphite substrate needs to be kept smooth, and plasma beam bombardment is used to remove residual impurities on the surface in order to obtain a two-dimensional thin film of axially grown carbon quantum bands with controllable stacking.

[0019] According to the technical solution of the present invention, after the sample is formed into a film, it is placed on a spin coater and the spin coating time is kept at 3500 rpm for 30 seconds. Then, it is quickly rinsed with a small amount of ethanol. If the sample and solvent with controllable stacked carbon quantum bands are not removed from the surface, a two-dimensional thin film with controllable stacked carbon quantum bands cannot be obtained.

[0020] The stacked, controllable, axially grown carbon quantum bands prepared by this invention have a wide absorption range and high electron mobility.

[0021] The stacked and controllable axially grown carbon quantum bands prepared by this invention have the characteristics of solution processability, high quantum yield, high charge transport and matching.

[0022] The method of this invention is simple, has a novel structure, and has superior performance. It is suitable for the preparation of two-dimensional thin films of carbon quantum bands with controllable axial growth through thermal stacking.

[0023] The two-dimensional thin film of axially grown carbon quantum bands prepared by this invention has a long exciton lifetime and diffusion distance, and high and balanced electron and hole mobility.

[0024] The two-dimensional thin film of axially grown carbon quantum bands prepared by this invention has broad application prospects in optoelectronic devices, biomedicine, and sensors. When used alone as an active layer in SCs, it offers advantages such as high device efficiency and stability compared to SCs prepared with CQDs that have high emission intensity and narrow absorption range. It is expected to serve as a low-cost, environmentally friendly novel organic active material for the SC field. Attached Figure Description

[0025] Figure 1 Aberration-corrected transmission electron microscope image of the stacked, controllable, axially grown carbon quantum bands prepared in Example 1;

[0026] Figure 2 The Fourier transform spectrum of the stacked, controllable, axially grown carbon quantum bands prepared in Example 1 is shown.

[0027] Figure 3 The X-ray diffraction spectrum of the stacked, controllable, axially grown carbon quantum bands prepared in Example 1 is shown.

[0028] Figure 4 The image shows the Raman spectrum of the stacked, controllable, axially grown carbon quantum bands prepared in Example 1.

[0029] Figure 5 The infrared spectrum of the stacked, controllable, axially grown carbon quantum bands prepared in Example 1;

[0030] Figure 6 X-ray photoelectron spectroscopy of the stacked, controllable, axially grown carbon quantum bands prepared in Example 1;

[0031] Figure 7 This is a fabrication diagram of the two-dimensional thin film of axially grown carbon quantum bands prepared in Example 2;

[0032] Figure 8 The absorption spectrum of the two-dimensional thin film of axially grown carbon quantum bands prepared in Example 2 is shown.

[0033] Figure 9 The time-resolved decay spectrum of the two-dimensional thin film of axially grown carbon quantum bands prepared in Example 2 is shown.

[0034] Figure 10 The electron density-voltage diagram of the electron and hole device of the stacked and controllably grown axial carbon quantum bands prepared in Example 2.

[0035] Figure 11 An atomic force microscopy image of the two-dimensional thin film of stacked, controllably grown carbon quantum bands prepared in Example 2;

[0036] Figure 12 High-resolution atomic mechanical microscope images of different stacking structures of two-dimensional thin films of axially grown carbon quantum bands prepared in Example 2;

[0037] Figure 13 FT images of different stacking structures of two-dimensional thin films of axially grown carbon quantum bands prepared in Example 2;

[0038] Figure 14 Height curves for different stacking structures of the two-dimensional thin film of axially grown carbon quantum bands prepared in Example 2;

[0039] Figure 15 Simulation diagrams of different stacking structures of two-dimensional thin films of axially grown carbon quantum bands prepared in Example 2;

[0040] Figure 16 The structure of the solar cell device prepared in Example 3;

[0041] Figure 17 The current density-voltage curve is shown for the solar cell device based on stacked, controllable axially grown carbon quantum bands prepared in Example 3.

[0042] Figure 18 The external quantum efficiency-wavelength curve of the solar cell device based on stacked and controllable axially grown carbon quantum bands prepared in Example 3 is shown.

[0043] Figure 19 The long-term operational stability of the solar cell device based on stacked, controllable axially grown carbon quantum bands prepared in Example 3;

[0044] Figure 20The photoelectric performance parameters of 20 devices based on stacked and controllable axially grown carbon quantum bands prepared in Example 3 are shown.

[0045] Figure 21 The diagram shows the efficiency distribution of the solar cell device based on stacked and controllably grown axial carbon quantum bands prepared in Example 3 under different seasons. Detailed Implementation

[0046] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0047] Example 1: Preparation of carbon quantum bands with controllable stacking and axial growth

[0048] Weigh 15-20 mg of 5,7,12,14-pentaphenyltetraone as a carbon source precursor, and sonicate it into 10 mL of formamide solvent to obtain a reaction mixture. Add 1-2 mL of concentrated sulfuric acid to promote the reaction of the precursor. Transfer the reaction mixture to a 25 mL polytetrafluoroethylene-lined stainless steel high-pressure reactor and tighten the lid. Solvothermal reaction at 220 °C for 6 hours, then allow to cool naturally to room temperature to obtain a dark red solution. Neutralize the solution to pH = 7 with sodium hydroxide, centrifuge to remove the supernatant, wash repeatedly with deionized water, and filter to obtain a black solid powder. Then, perform multiple column chromatography purifications using petroleum ether / ethyl acetate as the mobile phase to finally obtain a solid powder of axially grown carbon quantum bands with controllable stacking.

[0049] Typical aberration-corrected transmission electron microscope (AC-TEM) image ( Figure 1 The images clearly show that the stacked, controllably grown axial carbon quantum bands are hexagonal in shape with an aspect ratio of approximately 2:1, with a length distance of approximately 8.26 nm and a width of approximately 4.12 nm. The TEM images reveal a six-fold symmetric Fast Fourier Transform (FT) pattern. Figure 2 The presence of well-resolution lattice fringes with a spacing of 0.21 nm, corresponding to the (100) plane spacing, demonstrates a nearly defect-free crystal structure of axially grown carbon quantum bands with controllable stacking.

[0050] Powder X-ray diffraction patterns revealed a narrow (002) peak centered at approximately 24°, which differs from the ultrabroad peaks previously reported in CQDs, further indicating the high crystallinity of the stacked, controllable axially grown carbon quantum bands. Figure 3 Raman spectroscopy shows that at 1615 cm⁻¹… −1 The crystallization G band at this location is stronger than that at 1380 cm⁻¹ −1 The disordered D-band at the location ( Figure 4Fourier transform infrared spectroscopy indicates that the 3000-3600 cm⁻¹ range... −1 The broad absorption peaks in the region are related to the stretching of aromatic OH groups, with characteristic stretching vibration bands for C=O and C–O appearing at approximately 1630 and 1240 cm⁻¹, respectively. −1 place ( Figure 5 X-ray photoelectron spectroscopy (XPS) showed that AG-CQRs mainly contained C (~88%) and O (~12%). High-resolution XPS spectra of C1s and O1s further revealed the presence of C=C (~284.8 eV) and C=O (~532.4 eV). Figure 6 ).

[0051] Wherein, the volume-to-mass ratio of concentrated sulfuric acid to carbon source precursor (mL / mg) is any ratio between 1:10 and 1:15; the volume-to-mass ratio of formamide mixed solvent to carbon source precursor (mL / mg) is between 1:1.5 and 1:2.

[0052] Example 2: Preparation of two-dimensional thin films of carbon quantum bands with controllable stacking and axial growth

[0053] A 10 μL solution of chlorobenzene containing controllably stacked, axially grown carbon quantum bands was dropped onto the surface of a highly oriented pyrolytic graphite substrate. After the liquid had completely spread, excess liquid was absorbed with absorbent cotton. The substrate was then placed in a 10 μL container. -4 The sample was heated at 80°C for 15 minutes in a high vacuum atmosphere (Pa) to form a film. Figure 7 After the substrate has cooled to room temperature, it is placed on a spin coater and rapidly rinsed with ethanol at a speed of 3500 rpm for 30 seconds to obtain a two-dimensional thin film of axially grown carbon quantum bands with controllable stacking.

[0054] Two-dimensional thin films of axially grown carbon quantum bands with stacked controllable growth exhibit a wide absorption range (440-850 nm). Figure 8 The lifetime is approximately 1.8 μs, longer than that of previously reported CQDs with fluorescence emission. Its lifetime decreases with increasing temperature, and at low temperatures, the increased lifetime indicates that nonradiative processes are significantly suppressed. Figure 9 Furthermore, the thin film exhibits electron and hole mobilities as high as 2.03 × 10⁻⁶. −3 and 1.82 × 10 −3 cm 2 V −1 s −1 A balanced electron and hole mobility was achieved. Figure 10 ).

[0055] The above-mentioned large-scale scanning of the thin film revealed a series of sheet-like structures with dimensions of approximately 300-500 nm in high-resolution atomic force microscopy images. Figure 11 Further scanning of different sheet-like structures revealed four surface morphologies with different periodic lattice patterns. Figure 12 ), respectively corresponding to four characteristic FT patterns with highly resolved peaks ( Figure 13 Furthermore, four different height profiles were characterized with different periods of ~0.39, ~0.58, ~0.28, and ~0.63 nm. Figure 14 These properties are highly consistent with simulated structures of two axially grown carbon quantum bands with different stacking modes, typically defined as: AB stacking, AA stacking, SP-1 stacking, and SP-2 stacking. Figure 15 ).

[0056] Example 3: Preparation of two-dimensional thin films of carbon quantum bands based on stacked and controllable axially grown carbon quantum bands (SCs)

[0057] The two-dimensional thin film of axially grown carbon quantum bands prepared in Example 2 was applied alone as an active layer to SCs. Figure 16 As shown, the device structure, from bottom to top, includes a transparent glass substrate, an anode layer (ITO), a hole injection layer (poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS)), an active layer (a two-dimensional thin film of axially grown carbon quantum bands stacked and controlled), an interface layer (poly[(9,9-di(3'-(N,N-dimethylamino)propyl)fluorenyl-2,7-diyl)-ALT-[(9,9-di-n-octylfluorenyl-2,7-diyl)bromo(PFN-Br)), and a cathode layer (Al). The electroluminescent diode device structure is described as: ITO / PEDOT:PSS / CQDs / PFN-Br / Al.

[0058] The fabrication method of SCs devices is as follows:

[0059] (1) The transparent conductive substrate ITO glass was ultrasonically cleaned using acetone solution, isopropanol solution and deionized water. After cleaning, it was dried with dry nitrogen gas and then baked in an oven at 150 ºC for 10 minutes. The ITO on the glass substrate was used as the anode layer of the device.

[0060] (2) The dried substrate was transferred into a vacuum chamber and the ITO glass was subjected to ultraviolet ozone pretreatment for 15 min under oxygen pressure.

[0061] (3) Spin-coat PEDOT:PSS onto the treated ITO at 4000 rpm for 35 seconds. Then anneal in an oven at 150 ºC for 15 minutes;

[0062] (4) A two-dimensional thin film of stacked and controllably grown carbon quantum bands was prepared on a PEDOT:PSS layer;

[0063] (5) Spin-coat PFN-Br onto the active layer at a speed of 3500 rpm for 35 seconds;

[0064] (6) Then, the ITO was transferred to a nitrogen glove box. 100 nm Al was vacuum-deposited at a pressure of 3 × 10⁻⁶. -4 Pa, the evaporation rate was 0.3 nm / s, and the evaporation rate and thickness were monitored by a film thickness gauge;

[0065] (7) The device was not packaged; the current density-voltage characteristics of the device were tested directly, and the EQE parameters of the device were also tested.

[0066] Figure 17 The current density-voltage curves of SCs based on stacked, controllably grown carbon quantum bands in two-dimensional thin films are shown under simulated AM1.5 illumination. The highly overlapping curves of the forward and reverse scans demonstrate the low hysteresis of the device, which is attributed to the uniform and dense active layer. The open-circuit voltage (V0) is shown. oc The voltage is 0.59 V, and the short-circuit current density (J) is... sc The value is 5.35 mA cm⁻¹ −2 The fill factor (FF) was 38.64%, the maximum PCE was 1.22%, and the external quantum efficiency spectrum of the device was also measured. Figure 18 ).

[0067] The operational stability of unpackaged / packaged devices (exposed to sunlight and stored in a nitrogen atmosphere) is as follows: Figure 19 As shown in the figure, after continuous irradiation at 25°C for 120 h, the PCE of the unpackaged device decreased from 1.22% to 0.56%, retaining approximately 50% of its initial value. The packaged device maintained approximately 50% of its initial value after continuous irradiation at 25°C for 270 h, and exhibited excellent performance after a long period of continuous irradiation for 380 h. For the sake of operational repeatability, the performance parameter distribution of the 20 devices is statistically shown below. Figure 20 As shown. The device's PCE, FF, J SC and V OC The small variation compared to the average and the narrow distribution indicate that SCs based on stacked, controllably grown axial carbon quantum bands of two-dimensional thin films possess good device reproducibility, suggesting their potential for development in practical applications. The reproducibility of the device under all-weather indoor conditions is as follows:Figure 21 As shown, under different humidity conditions in four seasons, the SCs of two-dimensional thin films with controllable axial growth of carbon quantum bands exhibit low weather dependence and small performance differences, demonstrating good reproducibility. This result indicates that such devices can effectively block interference from environmental conditions and possess all-weather adaptability, showing great potential in various applications.

[0068] This embodiment is implemented based on the technical solution of the present invention, and provides detailed implementation methods and processes, but the protection scope of the present invention is not limited to the above embodiment.

Claims

1. Stacked, controllably grown axial carbon quantum ribbons, characterized in that, The stacked, controllable, axially grown carbon quantum bands are prepared through the following steps: Using 5,7,12,14-pentaphenyltetraone as a carbon source precursor, it was sonicated to dissolve in formamide solvent, and concentrated sulfuric acid was added to obtain a reaction mixture. The above reaction mixture was solvothermal reacted at 220 °C for 6 hours, and then naturally cooled to room temperature to obtain a crude product solution of the stacked and controllably grown axial carbon quantum bands; The crude product solution of the stacked, controllably grown axially carbon quantum ribbons was neutralized to pH 7, the supernatant was removed by centrifugation, washed with deionized water, and purified by column chromatography to obtain the solid powder of the stacked, controllably grown axially carbon quantum ribbons.

2. The stacked, controllable, axially grown carbon quantum ribbons according to claim 1, characterized in that, The volume-to-mass ratio of concentrated sulfuric acid to carbon source precursor (mL / mg) is 1:10 to 1:

15.

3. The stacked, controllable, axially grown carbon quantum ribbons according to claim 1, characterized in that, The volume-to-mass ratio of the formamide solvent to the carbon source precursor (mL / mg) is 1:1.5 to 1:

2.

4. A method for preparing the stacked, controllable, axially grown carbon quantum bands as described in claim 1, characterized in that, The method includes the following steps: Using 5,7,12,14-pentaphenyltetraone as a carbon source precursor, it was sonicated to dissolve in formamide solvent, and concentrated sulfuric acid was added to obtain a reaction mixture. The above reaction mixture was solvothermal reacted at 220 °C for 6 hours, and then naturally cooled to room temperature to obtain a crude product solution of the stacked and controllable axially grown carbon quantum bands. The crude product solution of the stacked, controllably grown axially carbon quantum ribbons was neutralized to pH 7, the supernatant was removed by centrifugation, washed with deionized water, and purified by column chromatography to obtain the solid powder of the stacked, controllably grown axially carbon quantum ribbons.

5. A method for preparing two-dimensional thin films of stacked, controllably grown axial carbon quantum bands, characterized in that, The method includes the following steps: A chlorobenzene solution of stacked, controllable, axially grown carbon quantum bands as described in claim 1 is dropped onto the surface of a highly oriented pyrolytic graphite substrate, fully spread, excess solution is absorbed, and the substrate is heated in a high vacuum environment to form a film. The film surface was cooled and rinsed with ethanol to obtain a two-dimensional thin film with axially grown carbon quantum bands that could be stacked and controlled.

6. The method for preparing a two-dimensional thin film of stacked, controllable axially grown carbon quantum bands according to claim 5, characterized in that, The chlorobenzene solution of the stacked, controllably grown axial carbon quantum bands was dropped into 10 -4 Film was formed by heating at 80 °C for 15 minutes in a high vacuum atmosphere.

7. The two-dimensional thin film of stacked, controllably grown axial carbon quantum bands as described in claim 5 is used to prepare solar cells.

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