Heraeus continues to strengthen its technology portfolio for the development of metallization paste for solar cells with their co-ownership with Shoei Chemical Inc. of patents TWI453930 and TWI432539. Both patents have a priority date of October 28, 2009. This co-ownership with Shoei provides Heraeus with a strong intellectual property position in the development, manufacturing and use of pastes having tellurium glass frit in the paste compositions. Along with Taiwan, these patents have granted counterparts in key pv markets such as the US, China and Japan.
Glass frit is a key component in the formulation of metallization pastes. Glass frit enables the bond between the silicon substrate and the metal conductor. The typical glass frit used is lead containing borosilicate glass. Though lead free glasses such as zinc borosilicate and bismuth borosilicate glass frits have been used, they do not possess the proper characteristics for ideal firing-through of the antireflective coating and contact formation to the silicon substrate. However, lead free tellurium glass frit has the benefits of a low melting point, and easily dissolves solid silver in solution. Metallization containing tellurium has also demonstrated improved electrical contact to silicon substrates.
“The integration of this technology from Shoei into our existing technology will allow Heraeus to even further improve the contacting characteristics of our existing pastes and our ability to provide the market with new pastes for crystalline solar cells”, according to Dr. Weiming Zhang of the Heraeus Photovoltaics Global Business Unit. He continues to state, “We will be able to develop higher preforming metallization pastes for a variety of cell applications. For example, the lower melting point of the tellurium glass frit provides advantages to PERC cell processing, which requires lower firing temperatures.”
The above mentioned patents have embodiments for the use of metallization pastes which include 25 to 90 mol% of tellurium oxide in the glass frit. These patents also concern the use of pastes having leaded or lead free tellurium glasses.
“Our goal is to develop and possess technologies that will add value to our customers’ products. The partnership with Shoei Chemical helps Heraeus strengthen our thick film and PV paste portfolio to deliver better products to our customers,” said Andreas Liebheit, Head of Heraeus Photovoltaics Global Business Unit. He also states, “Heraeus will continue its tradition of investment, innovation, technology development and collaboration for the advancement of the photovoltaics industry. The ultimate goal for the investments in technology made by Heraeus is to successfully provide a differential advantage for us and our customers, and we are willing to protect our rights against competition for the long term benefit of the industry.”