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Hongwu Nano is supplying high-tap density silver powder for solar photovoltaic cells in bulk

The basic structure of a crystalline silicon solar cell consists of a P-type silicon substrate, an n-type layer, an anti-reflection film (TiO2, SiO2 or Si3N4), a front silver electrode, a back aluminum electrode and a back silver electrode. The back-side silver electrode is an electrode formed by using silver conductive paste through screen printing and then sintering.

In the case of the same solid content, the different particle size, morphology, and ratio of silver powder would affect the viscosity performance. Tests show that the silver powder used in the back silver paste plays a key role in ensuring electrical performance, improving adhesion and welding power. In the case of low solid content, using a slurry prepared from micro-flaky silver powder, the resulting electrode film is dense and smooth, has excellent electrical properties, and good adhesion and welding properties.

The silver electrode paste on the light-receiving surface of solar cells uses high-performance metal conductive spherical silver powder.

The silver electronic paste used for the front electrode of silicon solar cell is mainly composed of three parts:
1. Superfine metallic silver powder with conductive effect. 70-80wt%. Ag powder has high photoelectric conversion efficiency.
2. Inorganic phase that plays a role of solidifying flux after heat treatment. 5-10wt%
3. The organic phase that acts as a binding agent at low temperatures. 15-20wt%

Ultra-fine silver powder is the main component of silver electronic paste, which ultimately forms the electrode of the conductive layer. Therefore, the particle size, shape, surface modification, specific surface area and tap density of silver powder have a greater impact on the performance of the slurry. The particle size of the silver powder used in the silver electronic paste is generally controlled within 0.2-3um, and the shape is spherical or quasi-spherical. If the particle size is too large, the viscosity and stability of the silver electronic paste will be significantly reduced, and because the gap between the particles is relatively large, the sintered electrode is not close enough, the contact resistance is significantly increased, and the mechanical properties of the electrode are also not ideal. If the particle size is too small, it is difficult to mix uniformly with other ingredients during the preparation of silver paste.

The silver coated copper powder materials prepared by Hongwu Nano’s technical engineers have relatively good sphericity, good dispersibility, uniform particle size, adjustable high tap density and superior electrical conductivity. The solar photovoltaic cell front electrode paste prepared by high-tap density silver powder has the characteristics of non-sticky rolls, easy printing, very small shrinkage, and dense sintered film, which fills the gap in the production of high-tap-density spherical silver powder in China.

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Conductive fillers (carbon nanotubes, silver powder, copper powder) and conductive inks

Conductive ink is a special conductive coating that has been developed rapidly with the emergence of modern printed electronic technology. Compared with electronic products manufactured by traditional conductive coatings, printed electronic products based on conductive inks are flexible, large-area, lot sizing, lightweight, low cost, and environmentally friendly, and the market prospects are broad. Carbon nanotubes have high conductivity and large aspect ratio. As a conductive filler, it is very easy to build a conductive path and an ideal conductive ink filler.

Conductive ink is a composite material composed of conductive fillers, resin binders, solvents, dispersion stabilizers and additives. Among them, conductive fillers are the key functional phase. According to the properties of conductive fillers, it can be divided into three categories: silver, copper, and carbon (carbon nanotubes, graphene).

The latest application of nano conductive ink:

1.Flexible transparent conductive film

Using nano silver conductive ink as the conductive raw material, latest manufacturing technology-nano imprinting technology to produce the flexible transparent conductive film to replace the traditional conductive film. The flexible transparent conductive film produced by this process has the following characteristics: the surface resistance and light transmittance of the film are adjustable, which is better than the ITO transparent conductive film; the patterned electrode can be realized at one time, the flexible substrate is used, and the roll-to-roll large area and batch can be realized. It can be manufactured at a low cost and achieve extremely high surface conductivity.

2.RFID antennas

As early as many years ago, some people began to study using nano conductive ink to print RFID antennas. Its biggest advantages are simple process, environmental protection, and low drying temperature (applicable to a variety of substrates). Commonly used RFID antennas are divided into high frequency and ultra high frequency. The high frequency antenna manufacturing process is relatively cumbersome, and the circuit needs to be bridged between the front and back; the UHF antenna only needs to be printed on the substrate once, and the chip can be obtained after drying, RFID tags. Therefore, the nano conductive ink printing UHF RFID antenna has more efficiency advantages.

3.Transistors

The benchmark for measuring the chip manufacturing process is the width of the connecting wires of the transistors in the chip, that is, the line width. The line width of a semiconductor chip is limited by the atomic size and has its physical limit. The chip volume cannot be infinitely small, and the frequency of power-on and power-off cannot be increased any more. Breaking through this bottleneck requires a thorough innovation in materials and technology. CNTs transistors can be used to replace silicon transistors. The performance of transistors made of CNTs is 3 to 5 times higher than that of traditional silicon transistors, and the production cost is low.

At present, some R&D institutions have begun to use carbon nanotubes conductive ink to print transistors. Use printing technology to make CNTs transistors on flexible substrates reach a practical level, and are used for RFID tags.

4.Paper battery

Paper batteries refer to ultra-thin batteries printed with conductive inks (mainly as electrodes) using paper or film substrates as carriers. The terminal products of paper batteries include active or semi-active RFID tags, tag sensors, smart cards, smart packaging, medical electronic drug stickers, etc..

Nano silver(Ag) conductive ink can also be applied to paper battery electrodes. Domestic manufacturers have also done this test, using nano silver conductive ink through inkjet printing to obtain electrodes on the PET film. After charging and discharging tests, it is found that it has better battery capacity and stable performance.

 

Conductive ink is an indispensable material for printed electronic devices, and is the key and core technology in the upstream of the printed electronics industry chain. It is believed that in the near future, large-scale flexible displays, environmentally friendly ultra-thin batteries, RFID tags, etc. will bring great convenience to people’s lives.

 

Hwnanomaterial is supplying conductive fillers for conductive inks in bulk, including silver, copper, silver-coated copper powder, carbon nanotubes, graphene, and so on. Welcome to contact us if you have any requirements!

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Four common metal conductive powders

Conductive materials can conduct current well because they have a large number of charged particles that can move freely under the action of an electric field, including conductor and superconducting materials.

The following are the four most widely used metal conductive materials.

Pure silver conductive powder (Ag99.99%)

1) Flake:

Common available particle size: <1um, 1-3um, 3-5um, 5-8um, 8-10um, particle size, and apparent density can be customized according to requirements. Flake silver powder with low apparent is available.

Appearance: silver gray with metallic luster

Application: Flake silver powder is a high-performance conductive filler material with good oxidation resistance. Flake Ag particle is the main raw material for making conductive coatings, membrane switches, conductive inks, conductive rubber, conductive plastics, and conductive ceramics.

Flake Ag powder is an ideal raw material for good low-temperature polymer slurry, conductive paint and electromagnetic shielding paint. The coating prepared with flake silver powder has good fluidity, anti-settling and large spray area.

2) Spherical silver conductive powder:

Common particle size: <1um, 1-3um, 3-5um，5-8um，etc

Application: Near-spherical silver powder is mainly used as conductive filler for high-temperature sintered conductive paste.

There is no absolute standard for silver powder as a conductive filler. The choice of silver powder should be based on the corresponding adhesive, the target conductor material, the physical and chemical properties of the film, and the reliability requirements.

 

Silver coated copper conductive powder (common particle size is 1-3um, 3-5um, 5-8um, 10um, Ag content ranges from 3%-35%)

Features:

1) Silver coated copper powder has adjustable superfine particle size.

2) Ag coated Cu powder has several shapes, such as spherical, flake, dendritic, etc.

3) Silver-coated copper powder has excellent conductivity and lower cost, which can replace some applications of pure silver powder.

4) Silver-coated copper powder has good oxidation resistance and dispersion, and can be used in medium and low temperature slurry.

Application range: It can be widely used in conductive adhesives, conductive coatings, polymer pastes, and various industries that require electrical conductivity and static electricity, electromagnetic shielding, and surface metallization of non-conductive materials.

Silver-coated copper powder can be widely used in conductive adhesives, conductive coatings, polymer pastes, and various fields of microelectronics technology that need to conduct electricity and static electricity, and non-conductive materials surface metallization. It is a new type conductive composite powder. Ag-Cu powder is widely used in the fields of electrical conductivity and electromagnetic shielding in various industries such as electronics, electromechanics, communications, printing, aerospace, and military industries, such as computers, mobile phones, integrated circuits, various electrical appliances, electronic medical equipment, electronic instruments, etc., so that products are not interfered by electromagnetic waves, while reducing the harm caused by electromagnetic radiation to the human body, as well as the conductivity of colloids, circuit boards, and other insulators, to make the insulated object have good electrical conductivity.

 

Pure copper powder (Cu 99%+)

Common particle size: <1um, 1-3um, 3-5um, 5-8um, etc.

Features: spherical and flake shape, uniform particle size, good dispersion, high crystallinity

Applications: Manufacture of terminals and internal electrodes of multilayer ceramic capacitors(MLCC), electronic components and electronic pastes, etc.

Pure nickel powder (Ni 99.7%): Common particle size: 1-3um

As a functional conductive filler, nickel powder can be added in coatings, adhesives, inks, plastics, rubbers, and can be made into conductive, electromagnetic shielding, anti-static  products, to be used in electronics, electromechanics, communications, printing, aerospace, weapons and other industrial sectors in the field of electrical conductivity. Such as computers, mobile phones, electronic medical equipment, electronic instruments and meters.

Guangzhou Hongwu Material Technology Co., Ltd. supplies the conductive materials mentioned above, with reliable high and stable quality, reasonable prices and excellent customized service.