Organic bulk heterojunction based photovoltaic multimodal gas sensor and method of fabrication

Abstract

The application discloses a photovoltaic multi-mode gas sensor based on an organic bulk heterojunction, which comprises an ITO electrode on a glass substrate, a hole transport layer coated on the glass substrate, an active layer and an electron transport layer coated on the hole transport layer in sequence, an AgNWs silver nanowire layer coated on the electron transport layer as a top electrode, and a lead wire made of conductive silver paste between the ITO electrode and the AgNWs silver nanowire layer. 71 A blended layer composed of BM, and the electron transport layer is PDINO.The application (1) changes the top electrode on the basis of the existing solar cell, and the manufacturing process is simple; (2) the application has the structure of the solar cell, and can fully absorb sunlight and generate a light signal under illumination; (3) when the application is used as a gas sensor device, the response and recovery time are relatively fast, and the detection of volatile organic compounds at the ppm level can be realized.

Description

Technical Field

[0001] This invention relates to the field of gas sensor technology, specifically to a photovoltaic multimodal gas sensor based on an organic bulk heterojunction and its fabrication method. Background Technology

[0002] Gas sensing converts information such as the composition, properties, and concentration of gases into easily analyzable signals (such as current and voltage), playing a crucial role in daily production and life. On one hand, the detection of hazardous gases in the external environment, including air pollution, flammable and explosive gases, indoor air quality, and the monitoring of pharmaceutical and food storage, all rely heavily on gas sensing. On the other hand, in emerging real-time, non-invasive smart healthcare, health status is monitored in real time by detecting gases with pathological indicators in human respiration; further development depends on high-performance and low-cost gas sensors. Based on these objectives, various types of gas sensors have been developed, mainly including resistive, optical, ultrasonic, acoustic, and electrochemical sensors. Sensors constructed from traditional inorganic metal oxide semiconductor materials typically require heating to higher temperatures to improve detection performance, which necessitates more complex device structures. The need for sensors to operate at higher temperatures significantly increases energy consumption, overall device size, and manufacturing costs. Furthermore, heating to high temperatures can alter the microstructure of the sensing nanomaterials, potentially leading to a decrease in sensing performance. On the other hand, due to the inherent sensitivity of organic materials to environmental variables such as light, heat, stress, gases, and biological analytes, sensors based on organic semiconductor materials have gradually become a research hotspot. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a photovoltaic multimodal gas sensor based on organic bulk heterojunction to overcome the shortcomings of the prior art, so as to achieve self-powered operation and identification of volatile organic compounds.

[0004] Another object of the present invention is to provide a method for fabricating the above-mentioned photovoltaic multimodal gas sensor based on organic bulk heterojunction.

[0005] The following technical solution is adopted to solve the technical problem of the present invention: A photovoltaic multimodal gas sensor based on an organic bulk heterojunction includes an ITO electrode on a glass substrate, a hole transport layer coated on the glass substrate, an active layer and an electron transport layer sequentially coated on the hole transport layer, and an AgNWs silver nanowire layer coated on the electron transport layer as the top electrode. Conductive silver paste leads the ITO electrode and the AgNWs silver nanowire layer. The hole transport layer is poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid)PEDOT:PSS, and the active layer is composed of 5T-X series molecules and PC. 71 The blend layer is composed of BM, and the electron transport layer is PDINO.

[0006] The hole transport layer has a thickness of 20-40 nm, the active layer has a thickness of 80-120 nm, the electron transport layer has a thickness of 10-15 nm, and the AgNWs silver nanowire layer has a thickness of 1-10 μm.

[0007] The hole transport layer, active layer, and electron transport layer are all formed using spin coating.

[0008] The hole transport layer is spin-coated and then annealed at 120-150℃ for 15-20 min.

[0009] The active layer is spin-coated and then annealed at 80-100℃ for 8-10 min.

[0010] The 5T-X series molecules and PC 71 The active layer of the BM blend consists of 5T-X series molecules and PC in a mass ratio of 1:0.8. 71 The coating is made by dissolving BM in chloroform to form a solution, wherein the total concentration of the solution is 10.8 mg / ml.

[0011] The structural formula of the 5T-X series molecules is as follows: .

[0012] PC 71 The structural formula of BM is: .

[0013] The above-mentioned method for fabricating a photovoltaic multimodal gas sensor based on an organic bulk heterojunction includes the following steps: (1) ITO electrodes were prepared on a glass substrate and ultrasonically cleaned in sequence with acetone, deionized water and isopropanol. Finally, the surface dust was blown away with N2. (2) Treat the ITO electrode on the glass substrate with O3 or O2 Plasma; (3) Spin-coat a water-soluble poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) PEDOT:PSS solution onto the glass substrate of the ITO electrode. The spin-coating speed is 3000-4500 r, the spin-coating time is 20-40 s, the thickness is 20-40 nm, and the solution is annealed at 120-150 °C for 15-20 min to form a hole transport layer. (4) 5T-X:PC 71 The BM active material is spin-coated onto the hole transport layer at a spin speed of 2000-4000 r, a spin time of 20-40 s, and a thickness of 80-120 nm. The active layer is then formed by annealing at 80-100℃ for 8-10 min. (5) Dissolve PDINO in methanol to obtain a 2 mg / ml solution and spin-coat it onto the active layer to form an electron transport layer. The spin-coating speed is 2000-3500 r, the spin-coating time is 20-40 s, and the thickness is 10-15 nm. (6) A 1% (w / w) solution of AgNWs dissolved in isopropanol was spin-coated onto the top of the electron transport layer to form a network structure of AgNWs silver nanowire layer as the top electrode. The spin-coating speed was 1000-2000 r, the time was 30-40 s, and the thickness was 1-10 μm. (7) Connect the bottom ITO electrode to the top electrode of the AgNWs silver nanowire layer with conductive silver paste.

[0014] In step (1), each ultrasonic cleaning session lasts 10-15 minutes.

[0015] In step (2), the ITO electrode on the glass substrate is treated with O3 or O2 Plasma for 20-30 minutes.

[0016] The photovoltaic multimodal gas sensor of this invention is based on the photovoltaic effect of the organic semiconductor small molecule active layer and the affinity between the organic semiconductor small molecules and volatile organic compounds. Multiple characteristic parameters, such as open-circuit voltage (Voc), short-circuit current (Jsc), fill factor (FF), and internal resistance, are extracted from the device in different gas environments using current-voltage curves. These parameters are used as sensing signals for volatile organic compounds. The sensor establishes the interaction mechanism between the active layer morphology, stacking structure, conjugation degree, and charge exchange, which are regulated by the organic molecular skeleton structure, side chain length, and terminal groups, thereby achieving accurate identification of various volatile organic compounds. Specifically, a hole transport layer is coated onto a glass substrate with an ITO electrode using spin coating. An active material is coated onto the hole transport layer to form the active layer of a gas-sensitive thin film. An electron transport layer is coated onto the active layer material using spin coating. An AgNWs solution is spin-coated onto the top as the top electrode. The photovoltaic multimodal gas sensor of this invention comprises a hole transport layer, an active layer of a gas-sensitive thin film, a gas-sensitive layer composed of an organic small-molecule photovoltaic donor-acceptor material for electron transport, a network of porous electrodes made of silver nanowires bonded to conductive silver paste as electrode B on top of the gas-sensitive layer, and a transparent electrode made of indium tin oxide bonded to conductive silver paste as electrode A on the bottom layer. Because organic photovoltaic small molecules possess abundant structural units, framework structures, organic functional groups, and stacking modes, the photoelectric signal they generate can be characterized using an IV scan curve, which displays multiple characteristic information such as open-circuit voltage, short-circuit current, fill factor, and internal resistance. By utilizing these characteristic information of the passive device, it can operate in multiple modes and monitor the target gas in the environment. This passive gas sensor can directly utilize the photovoltaic effect for gas monitoring, significantly reducing energy consumption, while also featuring a simple structure, easy fabrication, and convenient integration. This invention integrates solar energy collection and gas sensing functions into a single unit device. The patterned ITO electrode on the bottom glass substrate serves as the bottom electrode. The patterned ITO electrode has a fixed area, which is the effective area of ​​the battery. The bottom ITO electrode and the top AgNWs electrode serve as the positive and negative electrodes of the battery, respectively, and are connected to the gas sensing chamber. Under the illumination of the built-in light source, gas is introduced. Volatile organic compounds will enter the inner layer through AgNWs. The gas molecules to be measured will react with the inner layer material. Sunlight irradiation generates electron-hole pairs, which move to both sides under the action of the built-in electric field. The introduction of gas molecules causes the arrangement of the active layer to change, resulting in changes in photovoltaic parameters. Finally, the output signal of the sensor is the four photovoltaic parameters of the solar cell module: short-circuit current Jsc, open-circuit voltage Voc, fill factor FF, and power conversion efficiency PCE. (1) This invention changes the top electrode based on the existing solar cell, and the manufacturing process is simple. (2) This invention has the structure of a solar cell, and can fully absorb sunlight and generate light signals under illumination.(3) When this invention is used as a gas sensor, the response and recovery times are fast, and it can detect volatile organic compounds at the ppm level. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a response-time graph showing the change in resistance value of the gas sensor prepared in Example 1 of the present invention as a volatile organic compound is introduced. Figure 3 This is a graph showing the response of the gas sensor prepared in Example 1 of the present invention to the change of Voc value of a solar photovoltaic device module in 20 measurements as a volatile organic compound is introduced. Figure 4 This is a graph showing the response of the gas sensor prepared in Example 1 of the present invention to the change of the FF value of a solar photovoltaic device module in 20 measurements as a volatile organic compound is introduced. Figure 5 This is a graph showing the response of the gas sensor prepared in Example 1 of the present invention to the PCE value of a solar photovoltaic device module in 20 measurements as a volatile organic compound is introduced. Figure 6 This is a JV curve diagram of the device of the present invention; Figure 7 This is a schematic diagram of the energy harvesting principle of the present invention; Figure 8 This is a schematic diagram of the gas-sensitive detection principle of the present invention; Figure 9 This is a template image of a custom ITO electrode (the white part is the ITO electrode). Detailed Implementation

[0018] Example 1 A photovoltaic multimodal gas sensor based on an organic bulk heterojunction includes a 1.5cm × 1.5cm glass substrate, on which three 0.06cm² areas are deposited. 2 The ITO electrode, the structure of the ITO electrode is as follows Figure 9 As shown. A hole transport layer with a thickness of 30 nm was spin-coated onto a glass substrate. The hole transport layer was made of poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid) PEDOT:PSS. An active layer and an electron transport layer were sequentially coated on the hole transport layer. The active layer was made of 5T-CN:PC. 71 BM is composed of 5T-CN series molecules and PC in a mass ratio of 1:0.8. 71The electrode was coated with a solution of BM dissolved in chloroform, with a total concentration of 10.8 mg / ml. The active layer was 120 nm thick, the electron transport layer was PDINO with a thickness of 10 nm, and an AgNWs silver nanowire layer with a thickness of 5 μm was coated on the electron transport layer as the top electrode.

[0019] The above-mentioned method for fabricating a photovoltaic multimodal gas sensor based on an organic bulk heterojunction includes the following steps: (1) ITO electrodes were prepared on a glass substrate and ultrasonically cleaned in sequence with acetone, deionized water and isopropanol for 10 min each time. Finally, the surface dust was blown away with N2. (2) Treat the ITO electrode on the glass substrate with O2 Plasma for 30 min; (3) A water-soluble poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) PEDOT:PSS solution was spin-coated onto the glass substrate of the ITO electrode at a spin speed of 3000 r, a spin time of 40 s, and a thickness of 30 nm. The solution was then annealed at 120 °C for 20 min to form a hole transport layer. (4) Composed of 5T-CN series molecules and PC in a mass ratio of 1:0.8 71 A solution of BM dissolved in chloroform, with a total concentration of 10.8 mg / ml, was prepared by adding 5T-CN:PC. 71 The BM active material solution was spin-coated onto the hole transport layer at a spin speed of 2000 r, a spin time of 20 s, and a thickness of 120 nm. The active layer was then annealed at 80 °C for 8 min to form the active layer. (5) PDIN was dissolved in methanol and then spin-coated onto the active layer to form an electron transport layer. The ratio of PDIN to methanol was 2 mg / ml. The spin-coating speed was 3500 r, the spin-coating time was 40 s, and the thickness was 10 nm. (6) A 1% (w / w) solution of AgNWs dissolved in isopropanol was spin-coated onto the top of the electron transport layer to form a network structure of AgNWs silver nanowires as the top electrode. The spin-coating speed was 1000 r, the time was 30 s, and the thickness was 5 μm. The gas to be measured is introduced into the chamber where the device is placed. It can be seen that as the gas is introduced, the resistance decreases and the current increases. The response value R (defined as the ratio of the change in current from the initial current to the response current to the initial current versus the measurement time) is plotted. It can be seen that the response values ​​all exceed 4%, and the difference in response values ​​is small across multiple cycles, indicating that the device has good cycle performance. Figure 4 , Figure 5 , Figure 6 For photovoltaic multimodal gas sensor V OCThe change in the PCE response value with the number of measurements is defined as the change in V before and after the introduction of the test gas, n-heptanal. OC The graph shows the ratios of the changes in FF and PCE values ​​to their values ​​before the gas to be tested was introduced. It can be seen from the graph that the Voc value response is around 6%, the FF value response is 3%-4%, and the PCE value response can reach more than 10%.

[0020] Example 2 A photovoltaic multimodal gas sensor based on an organic bulk heterojunction, such as Figure 9 The diagram shows a 1.5cm x 1.5cm glass substrate, on which three 0.06cm² areas are deposited. 2 The ITO electrode, the structure of the ITO electrode is as follows Figure 9 As shown. A hole transport layer with a thickness of 40 nm is deposited on a glass substrate. The hole transport layer is poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid)PEDOT:PSS. An active layer and an electron transport layer are sequentially coated on the hole transport layer. The active layer is 5T-CAO:PC. 71 BM is composed of 5T-CAO series molecules and PC in a mass ratio of 1:0.8. 71 The electrode was coated with a solution of BM dissolved in chloroform, with a total concentration of 10.8 mg / ml. The active layer was 120 nm thick, the electron transport layer was PDINO with a thickness of 10 nm, and an AgNWs silver nanowire layer with a thickness of 10 μm was coated on the electron transport layer as the top electrode.

[0021] The above-mentioned method for fabricating a photovoltaic multimodal gas sensor based on an organic bulk heterojunction includes the following steps: (1) Prepare an ITO electrode on a glass substrate and clean it with acetone, deionized water and isopropanol in sequence. Each ultrasonic cleaning lasts for 15 minutes. Finally, blow away the dust on the surface with N2. (2) Treat the ITO electrode on the glass substrate with O2 Plasma for 20 min; (3) A water-soluble poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) PEDOT:PSS solution was spin-coated onto the glass substrate of the ITO electrode at a spin speed of 4500 r, a spin time of 20 s, and a thickness of 40 nm. The solution was then annealed at 150 °C for 15 min to form a hole transport layer. (4) Composed of 5T-CAO series molecules in a mass ratio of 1:0.8 and PC 71 A solution of BM dissolved in chloroform, with a total concentration of 10.8 mg / ml, was prepared by adding 5T-CAO:PC. 71The BM active material solution was spin-coated onto the hole transport layer at a spin speed of 4000 r, a spin time of 40 s, and a thickness of 120 nm. The active layer was then annealed at 100 °C for 10 min. (5) PDINO was dissolved in methanol and then spin-coated onto the active layer to form an upper electron transport layer. The ratio of PFN-Br to methanol was 2 mg / ml. The spin-coating speed was 2000 r, the spin-coating time was 20 s, and the thickness was 10 nm. (6) A 1% (w / w) solution of AgNWs dissolved in isopropanol was spin-coated onto the top of the electron transport layer to form a network structure of AgNWs silver nanowires as the top electrode. The spin-coating speed was 2000 r, the time was 40 s, and the thickness was 10 μm.

[0022] The principle of the energy harvesting part of this invention is as follows: Figure 6 As shown, the process includes ① light absorption and exciton generation, ② exciton diffusion, ③ exciton separation, ④ charge transport, and ⑤ charge collection. Process ① involves the active layer material absorbing photons of specific energy under sunlight, generating hole-electron pairs. Process ② involves excitons freely diffusing to the donor-acceptor interface. Process ③ involves excitons diffusing to the donor-acceptor interface to form charge-transfer states, where charge separation occurs under the influence of the built-in electric field: excitons on the donor molecule transfer charge to the LUMO level of the acceptor molecule, while holes remain at the HOMO level; excitons on the acceptor molecule transfer holes to the HOMO level, while electrons remain at the LUMO level. Process ④ involves excitons separating into free charges, and the resulting holes and electrons transported in the donor and acceptor phases respectively under the influence of the internal electric field, subsequently reaching the interface between the active layer and the electrode. Process ⑤ involves holes and electrons transported to the anode and cathode respectively, then collected by the corresponding electrodes, entering the external circuit, and generating a photocurrent.

[0023] The gas detection mechanism of this invention is as follows: Figure 7 The arrangement shown changes, and the photovoltaic parameters of the energy harvesting section, such as the open-circuit voltage V, change. OC Short-circuit current J SC The fill factor (FF) and other parameters will change. When the gas to be tested enters the sensitive material, it causes a change in the arrangement of donors and acceptors inside the active layer, which in turn changes the photovoltaic parameters of the energy harvesting section, such as open-circuit voltage, short-circuit current, and fill factor.

[0024] Example 3 A photovoltaic multimodal gas sensor based on an organic bulk heterojunction, such as Figure 9 The diagram shows a 1.5cm x 1.5cm glass substrate, on which three 0.06cm² areas are deposited. 2 The battery uses ITO electrodes, therefore the battery area is 0.06 cm².2 A hole transport layer with a thickness of 20 nm is deposited on a glass substrate. The hole transport layer is poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid)PEDOT:PSS. An active layer and an electron transport layer are sequentially coated on the hole transport layer. The active layer is 5T-RD:PC. 71 The active layer of the BM is 80 nm thick, the electron transport layer is PDINO with a thickness of 15 nm, and an AgNWs silver nanowire layer is coated on the electron transport layer as the top electrode with a thickness of 1 μm.

[0025] The above-mentioned method for fabricating a photovoltaic multimodal gas sensor based on an organic bulk heterojunction includes the following steps: (1) ITO electrodes were prepared on a glass substrate and ultrasonically cleaned in sequence with acetone, deionized water and isopropanol for 10 min each time. Finally, the surface dust was blown away with N2. (2) Treat the ITO electrode on the glass substrate with O3 for 30 min; (3) A water-soluble poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid)PEDOT:PSS solution was spin-coated onto the glass substrate of the ITO electrode at a spin speed of 3000 r, a spin time of 40 s, and a thickness of 20 nm. The solution was then annealed at 120 °C for 20 min to form a hole transport layer. (4) Composed of 5T-RD series molecules and PC in a mass ratio of 1:0.8 71 A solution of BM dissolved in chloroform, with a total concentration of 10.8 mg / ml, was prepared by adding 5T-RD:PC. 71 The BM active material solution was spin-coated onto the hole transport layer at a spin speed of 2000 r, a spin time of 20 s, and a thickness of 80 nm. The active layer was then annealed at 80 °C for 8 min to form the active layer. (5) PDINO was dissolved in methanol and then spin-coated onto the active layer to form an upper electron transport layer. The ratio of PDINO to methanol was 2 mg / ml. The spin-coating speed was 3500 r, the spin-coating time was 40 s, and the thickness was 15 nm. (6) A 1% (w / w) solution of AgNWs dissolved in isopropanol was spin-coated onto the top of the electron transport layer to form a network structure of AgNWs silver nanowires as the top electrode. The spin-coating speed was 1000 r, the time was 30 s, and the thickness was 1 μm.

Claims

1. A photovoltaic multimodal gas sensor based on an organic bulk heterojunction, characterized in that: The structure includes an ITO electrode on a glass substrate, a hole transport layer coated on the glass substrate, an active layer and an electron transport layer sequentially coated on the hole transport layer, and an AgNWs silver nanowire layer coated on the electron transport layer as the top electrode. Conductive silver paste leads the ITO electrode and the AgNWs silver nanowire layer. The hole transport layer is made of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid)PEDOT:PSS, and the active layer is composed of 5T-X series molecules and PC. 71 The blend layer is composed of BM, and the electron transport layer is PDINO; The hole transport layer has a thickness of 20-40 nm, the active layer has a thickness of 80-120 nm, the electron transport layer has a thickness of 10-15 nm, and the AgNWs silver nanowire layer has a thickness of 1-10 μm. The hole transport layer, active layer, and electron transport layer are all formed using spin coating. The hole transport layer is spin-coated and then annealed at 120-150℃ for 15-20 min; the active layer is spin-coated and then annealed at 80-100℃ for 8-10 min. The 5T-X series molecules and PC 71 The active layer of the BM blend consists of 5T-X series molecules and PC in a mass ratio of 1:0.

8. 71 The coating is made by dissolving BM in chloroform to form a solution, wherein the total concentration of the solution is 10.8 mg / ml.

2. The method for fabricating a photovoltaic multimodal gas sensor based on an organic bulk heterojunction according to claim 1, characterized in that... Includes the following steps: (1) ITO electrodes were prepared on a glass substrate and ultrasonically cleaned in sequence with acetone, deionized water and isopropanol. Finally, the surface dust was blown away with N2. (2) Treat the ITO electrode on the glass substrate with O3 or O2 Plasma; (3) Spin-coat a water-soluble poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) PEDOT:PSS solution onto the glass substrate of the ITO electrode. The spin-coating speed is 3000-4500 r, the spin-coating time is 20-40 s, the thickness is 20-40 nm, and the solution is annealed at 120-150 °C for 15-20 min to form a hole transport layer. (4) 5T-X:PC 71 The BM active material is spin-coated onto the hole transport layer at a spin speed of 2000-4000 r, a spin time of 20-40 s, and a thickness of 80-120 nm. The active layer is then formed by annealing at 80-100℃ for 8-10 min. (5) Dissolve PDINO in methanol to obtain a 2 mg / ml solution and spin-coat it onto the active layer to form an electron transport layer. The spin-coating speed is 2000-3500 r, the spin-coating time is 20-40 s, and the thickness is 10-15 nm. (6) A 1% (w / w) solution of AgNWs dissolved in isopropanol was spin-coated onto the top of the electron transport layer to form a network structure of AgNWs silver nanowire layer as the top electrode. The spin-coating speed was 1000-2000 r, the time was 30-40 s, and the thickness was 1-10 μm. (7) Connect the bottom ITO electrode to the top electrode of the AgNWs silver nanowire layer with conductive silver paste.

3. The method for fabricating a photovoltaic multimodal gas sensor based on an organic bulk heterojunction according to claim 2, characterized in that: In step (1), each ultrasonic cleaning session lasts 10-15 minutes.

4. The method for fabricating a photovoltaic multimodal gas sensor based on an organic bulk heterojunction according to claim 3, characterized in that: In step (2), the ITO electrode on the glass substrate is treated with O3 or O2 Plasma for 20-30 minutes.

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