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Article source: Frontiers of Materials Science? As an important optoelectronic material, transparent conductive film (TCF) has a wide range of applications in electronic and optoelectronic devices such as touch screens, flat panel displays, photovoltaic cells, and organic light-emitting diodes
.
At present, indium tin oxide (ITO) is the most widely used transparent conductive film material in the industry
.
The commonly used ITO preparation process involves high temperature and high vacuum energy consumption and complex processes
.
In addition, ITO is a brittle metal oxide and indium resources are scarce, making it increasingly difficult to meet the needs of technological development, especially for the new generation of flexible electronic devices
.
Single-walled carbon nanotubes have excellent mechanical, electrical and optical properties, so they are considered to be one of the most competitive flexible transparent conductive materials
.
The preparation methods of carbon nanotube transparent conductive film are mainly divided into wet method and dry method
.
Wet method refers to dispersing carbon nanotubes in a suitable solvent and depositing them on the corresponding substrate by methods such as suction filtration, dip coating, spray coating, or spin coating; dry method refers to directly growing carbon nanotubes by chemical vapor deposition (CVD) The tube film or the carbon nanotube array is drawn into a film
.
Figure 1.
Continuous preparation (left) and collection (right) of CNT thin films.
Group A05, Advanced Materials and Structure Analysis Laboratory, Institute of Physics, Chinese Academy of Sciences/Beijing National Research Center for Condensed Matter Physics, has long been committed to the preparation and physical properties of carbon nanostructures And applied basic research
.
Under the guidance of researcher Zhou Weiya and academician Xie Sishen, Dr.
Zhang Qiang of this research group, together with senior engineers Wang Yanchun, graduate students Xia Xiaogang, Li Kewei, Dr.
Zhang Nan, Dr.
Xiao Zhuojian, Dr.
Fan Qingxia, etc.
, developed a new type of continuous direct preparation of large area The method of self-supporting transparent conductive carbon nanotube (CNT) film-inflation aerosol method (BACVD), and applied for invention patent (ZL 201310164499.
5, ZL 201811117042.
8, PCT patent US 10,144,647 B2)
.
Based on BACVD, the output of CNT TCFs can reach hundreds of meters per hour and the carbon conversion rate (the rate of conversion from carbon source to CNT) can exceed 10%, which is higher than the corresponding index of traditional floating catalytic chemical vapor deposition (FCCVD) preparation of CNT TCFs 3 orders of magnitude higher
.
Figure 2.
Phase diagram of BACVD method (left), performance comparison of CNT samples prepared under different conditions (middle), comparison of yield and carbon conversion rate of CNT transparent conductive film prepared by BACVD method and traditional FCCVD method (right)
.
? BACVD is developed under the inspiration of the blown film preparation process and the floating catalytic chemical vapor technology.
Its mechanism is to use a special CNT synthesis reactor to realize the "blowing" process in the process of preparing CNTs by the FCCVD method
.
The specific preparation process includes two steps.
First, the aerosol bubble of the CNT is stably inflated, and then the aerosol bubble is "cured" into an aerogel by increasing the length of the CNT during the CNT growth process
.
Finally, the CNT transparent conductive film is ejected from the end of the reactor along with the carrier gas
.
Figure 3.
Performance and micro-morphology of CNT films prepared by BACVD method: light transmittance and sheet resistance (top left), stability (top right), scanning electron microscope (bottom left) and transmission electron microscope (bottom right) images
.
? The research team thoroughly studied the preparation process and gave a generalized phase diagram of the BACVD method
.
According to the specific preparation conditions, the phase diagram is divided into four regions, corresponding to different products
.
This phase diagram has guiding significance for further understanding of BACVD and film performance improvement
.
In addition, the method can realize the synthesis of thin films without hydrogen, which means that the preparation process is safe and efficient
.
The prepared thin film with a light transmittance of 90%, after simple doping, has a sheet resistance of about 40 ohm/sq, showing excellent photoelectric properties
.
For the ultra-thin CNT film prepared by BACVD, they designed a "roll" collection device to achieve continuous online collection of the film
.
Related research results were published on Advanced Materials (10.
1002/adma.
202004277)
.
In the process of writing the thesis, Prof.
Esko Kauppinen of Aalto University in Finland gave constructive opinions from the perspective of aerosol
.
Figure 4.
Continuous preparation and collection of CNT fibers (left) and their macro (middle) and micro (right) morphologies? In addition to CNT TCFs, the research team also used this method to conduct research on highly conductive and high-strength fibers
.
The prepared cylindrical film can be directly converted into continuous CNT fibers through a liquid shrinking agent
.
Then, through acid treatment, the performance of the fiber has been greatly improved
.
Especially after chlorosulfonic acid treatment, the strength of the fiber reached 2 GPa, while the electrical conductivity reached 4.
3 MS/m
.
Related research was published in Chinese Physics B (Chinese Physics B 26.
2 (2017): 28802-028802.
The
BACDV method, as a new method for preparing CNT thin films, is of great significance in basic research and industrial applications
.
This work proposes a A new idea for the construction of a new CNT macro-body-first use airflow to assist in the construction of a specific form of short CNT aerosol, and then combine the synthesis of CNTs to use the continuous increase in the length of the carbon tube to achieve the solidification of the aerosol
.
In addition, the ultra-high The output and carbon conversion rate of CNTs are of great significance to the industrialization of CNTs, especially for CNTs as “engineering materials” such as transparent conductive films, electrodes, and fibers
.
This work was approved by the Ministry of Science and Technology (2018YFA0208402, 2012CB932302), the National Natural Science Foundation of China (11,634,014, 51,172,271, 51,372,269) class a CAS support and pilot projects (XDA09040202), etc.
.
.
At present, indium tin oxide (ITO) is the most widely used transparent conductive film material in the industry
.
The commonly used ITO preparation process involves high temperature and high vacuum energy consumption and complex processes
.
In addition, ITO is a brittle metal oxide and indium resources are scarce, making it increasingly difficult to meet the needs of technological development, especially for the new generation of flexible electronic devices
.
Single-walled carbon nanotubes have excellent mechanical, electrical and optical properties, so they are considered to be one of the most competitive flexible transparent conductive materials
.
The preparation methods of carbon nanotube transparent conductive film are mainly divided into wet method and dry method
.
Wet method refers to dispersing carbon nanotubes in a suitable solvent and depositing them on the corresponding substrate by methods such as suction filtration, dip coating, spray coating, or spin coating; dry method refers to directly growing carbon nanotubes by chemical vapor deposition (CVD) The tube film or the carbon nanotube array is drawn into a film
.
Figure 1.
Continuous preparation (left) and collection (right) of CNT thin films.
Group A05, Advanced Materials and Structure Analysis Laboratory, Institute of Physics, Chinese Academy of Sciences/Beijing National Research Center for Condensed Matter Physics, has long been committed to the preparation and physical properties of carbon nanostructures And applied basic research
.
Under the guidance of researcher Zhou Weiya and academician Xie Sishen, Dr.
Zhang Qiang of this research group, together with senior engineers Wang Yanchun, graduate students Xia Xiaogang, Li Kewei, Dr.
Zhang Nan, Dr.
Xiao Zhuojian, Dr.
Fan Qingxia, etc.
, developed a new type of continuous direct preparation of large area The method of self-supporting transparent conductive carbon nanotube (CNT) film-inflation aerosol method (BACVD), and applied for invention patent (ZL 201310164499.
5, ZL 201811117042.
8, PCT patent US 10,144,647 B2)
.
Based on BACVD, the output of CNT TCFs can reach hundreds of meters per hour and the carbon conversion rate (the rate of conversion from carbon source to CNT) can exceed 10%, which is higher than the corresponding index of traditional floating catalytic chemical vapor deposition (FCCVD) preparation of CNT TCFs 3 orders of magnitude higher
.
Figure 2.
Phase diagram of BACVD method (left), performance comparison of CNT samples prepared under different conditions (middle), comparison of yield and carbon conversion rate of CNT transparent conductive film prepared by BACVD method and traditional FCCVD method (right)
.
? BACVD is developed under the inspiration of the blown film preparation process and the floating catalytic chemical vapor technology.
Its mechanism is to use a special CNT synthesis reactor to realize the "blowing" process in the process of preparing CNTs by the FCCVD method
.
The specific preparation process includes two steps.
First, the aerosol bubble of the CNT is stably inflated, and then the aerosol bubble is "cured" into an aerogel by increasing the length of the CNT during the CNT growth process
.
Finally, the CNT transparent conductive film is ejected from the end of the reactor along with the carrier gas
.
Figure 3.
Performance and micro-morphology of CNT films prepared by BACVD method: light transmittance and sheet resistance (top left), stability (top right), scanning electron microscope (bottom left) and transmission electron microscope (bottom right) images
.
? The research team thoroughly studied the preparation process and gave a generalized phase diagram of the BACVD method
.
According to the specific preparation conditions, the phase diagram is divided into four regions, corresponding to different products
.
This phase diagram has guiding significance for further understanding of BACVD and film performance improvement
.
In addition, the method can realize the synthesis of thin films without hydrogen, which means that the preparation process is safe and efficient
.
The prepared thin film with a light transmittance of 90%, after simple doping, has a sheet resistance of about 40 ohm/sq, showing excellent photoelectric properties
.
For the ultra-thin CNT film prepared by BACVD, they designed a "roll" collection device to achieve continuous online collection of the film
.
Related research results were published on Advanced Materials (10.
1002/adma.
202004277)
.
In the process of writing the thesis, Prof.
Esko Kauppinen of Aalto University in Finland gave constructive opinions from the perspective of aerosol
.
Figure 4.
Continuous preparation and collection of CNT fibers (left) and their macro (middle) and micro (right) morphologies? In addition to CNT TCFs, the research team also used this method to conduct research on highly conductive and high-strength fibers
.
The prepared cylindrical film can be directly converted into continuous CNT fibers through a liquid shrinking agent
.
Then, through acid treatment, the performance of the fiber has been greatly improved
.
Especially after chlorosulfonic acid treatment, the strength of the fiber reached 2 GPa, while the electrical conductivity reached 4.
3 MS/m
.
Related research was published in Chinese Physics B (Chinese Physics B 26.
2 (2017): 28802-028802.
The
BACDV method, as a new method for preparing CNT thin films, is of great significance in basic research and industrial applications
.
This work proposes a A new idea for the construction of a new CNT macro-body-first use airflow to assist in the construction of a specific form of short CNT aerosol, and then combine the synthesis of CNTs to use the continuous increase in the length of the carbon tube to achieve the solidification of the aerosol
.
In addition, the ultra-high The output and carbon conversion rate of CNTs are of great significance to the industrialization of CNTs, especially for CNTs as “engineering materials” such as transparent conductive films, electrodes, and fibers
.
This work was approved by the Ministry of Science and Technology (2018YFA0208402, 2012CB932302), the National Natural Science Foundation of China (11,634,014, 51,172,271, 51,372,269) class a CAS support and pilot projects (XDA09040202), etc.
.
