Cu Paste/Barrier

As experts in materials, we are the first in the world to succeed in commercializing a "copper paste" to replace silver pastes for solar cells.

copper paste

Increased adoption of solar energy at a lower cost for a sustainable society

The demand for solar energy is growing today as an alternative for exhaustible resources, and to address and mitigate global warming. The cost of solar power generation equipment must decrease in order to realize wider adoption of solar energy and its self-sustaining growth.

Manufacturers currently use silver (Ag) pastes to form wires and electrodes on the surface of solar battery cells. Silver pastes, which contain more than 90% silver particles, make up approximately 10 to 30% of the material cost of these cells. However, the high cost of silver and its volatile pricing is a disadvantage for both manufacturers and consumers.

R&D and technology to overcome major hurdles for copper paste

Research and development has long been conducted to find ways of reducing the amount of silver used in manufacturing, but limitations exist. Researchers have turned to the possibility of using low-cost copper pastes, since copper has roughly the same conductivity as silver at 1/100th the cost. However, there are significant hurdles in realizing a commercially viable copper paste because copper diffuses in silicon, affecting the properties of the solar cells. Furthermore, copper oxidizes during sintering, causing the resistance to increase.

The Koike Lab of the Department of Materials Science, Graduate School of Engineering, Tohoku University has successfully developed a diffusion barrier layer formed between a silicon wafer and copper wires, and identified sintering conditions that prevent copper paste from oxidizing. The commercialization of this technology leapfrogs more than 20 years of efforts by the world's leading manufacturers.

Junichi Koike

Junichi Koike
CTO and Founder

He is currently a professor at the Department of Material Science, Tohoku University. He received B. Eng. and M.Eng. in Metallurgy from Tokyo Institute of Technology and Ph.D. in Materials Science from Northwestern University. He was a graduate research assistant at Argonne National Laboratory, a director postdoctoral fellow at the Center of Materials Science, Los Alamos National Laboratory, and an assistant professor at Oregon State University. He joined Tohoku University as an associate professor in 1994 and has been a full professor since 2005. His research activity focuses on the development of new materials and processes for nano-scale interconnections in advanced semiconductor devices. Collaboration with world-wide partners had led to the development of a novel Cu alloy that is now a de-facto standard for advanced silicon chips. His recent research interest is Cu metallization for solar cells. He made a numerous numbers of invited presentations and tutorial talks at international conferences, and published over 150 papers in peer reviewed journals and conference proceedings.