Replacing Lead Oxide with Tungsten Trioxide Improves the Performance of Photovoltaic Front Silver Paste

The silver paste for the front electrode of solar cells is one of the main raw materials that affect the electrical properties of solar cells. The photovoltaic front silver paste is mainly composed of three parts: conductive phase, organic term and inorganic term. 

The conductive item is the metal powder with conductive function, generally the silver micropowder with the best conductivity is used; the organic phase is the organic carrier suitable for screen printing technology, and the organic carrier is mainly composed of organic solvents, plasticizers, thixotropic agents, and leveling agents. Inorganic components are mainly composed of low glass powder and metal oxides, which play the role of fire-through antireflection layer and bonding.

Most of the traditional solar cell front electrode silver pastes use low-melting glass powder containing lead oxide PbO, mainly because PbO can significantly reduce the softening temperature of glass powder, and lead oxide-containing glass powder has good wettability with the matrix material. Silver is powerful. However, lead not only pollutes the environment, but also has great harm to the human body. To prepare an environmentally friendly lead-free solar cell front electrode silver paste, the key is to develop lead-free glass powder, which can replace the lead-containing glass powder and ensure the performance of the paste.

Tungsten trioxide is an inorganic chemical raw material and the most common oxide of tungsten. It has the advantages of high specific gravity, large specific surface area, non-toxic and harmless, and has been used to replace lead oxide as an additive to glass powder. Experiments have proved that the glass powder added with tungsten trioxide maintains the performance of the existing technology, and at the same time, the glass has low viscosity and good wettability with other components, and improves the characteristics of the front electrode silver paste glass, such as viscosity, softening temperature, chemical stability, glass transition point, linear expansion coefficient, etc.

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