Metallization

Increasing prices may prompt module manufacturers to find alternatives, or at least reduce silver use in solar cell metallization, according to a recent study. Researcher Samuele Lo Piano, however, told pv magazine silver availability does not represent an issue for large scale PV. Copper-nickel alloys may offer an alternative, he added, but there could be a long wait for them to be viable.

Silver demand for PV production worldwide is forecast to grow to 105 million ounces this year, as overall demand hits an eight-year high. Prices for the precious metal could reach a seven-year high of $30.00 per ounce this year but, according to the Silver Institute, this level is still far away from any critical threshold that would make silver supply for the solar industry problematic.

In a new paper published in the journal of Renewable and Sustainable Energy, renowned PV scientist Pierre Verlinden examines the solar industry’s trajectory towards the 70 TW of installed capacity that will be needed by 2050, as the best choice for meeting climate targets set out in the 2015 Paris agreement. Silver consumption and recycling, according to Verlinden, will be the biggest challenges in the years to come, as well as ensuring balanced growth and avoiding a major installation rush in the years close to 2050.

Scientists led by staff from Germany’s Fraunhofer ISE have demonstrated a new laser printing process in pilot production, which could replace silver paste and screen printing in solar cell manufacturing. The system is said to offer much more flexibility in the layout of contact fingers on the cell surface and a wider choice of metallization materials.

The system can metallize the front and back sides of silicon solar cells with unprecedented precision and speed, Fraunhofer ISE said. The technology is also suitable for components such as printed circuit boards or chip cards.

An international research team has defined the operational parameters needed to design and manufacture crystalline silicon PV modules for tropical climates. The group proposed a back-junction, back-contact cell tech with a selective laser soldering technique it claims offers the best potential to yield such robust panels.

Trade body the Silver Institute says silver demand in the solar industry will dip slightly this year but remain near to previous record highs. Silver paste consumption for PV has been reduced due to advances in metallization techniques.

The efficiency of the cell, made with a standard M2 wafer, was raised around 0.7% by using an improved busbar-free screen printing metallization process based on heterojunction processes developed with manufacturing equipment provided by Swiss specialist Meyer Burger.

Researchers in Korea have proposed a new design for dividing and bonding which is said to provide higher efficiency from fewer fingers. The number of fingers optimized for division into five cells was 128 and for three, 171. Five offer power conversion efficiency of 17.346% and three 16.855%.

A U.S. research group has developed a metal-carbon-nanotube composite – MetZilla – which can be embedded in commercial, screen-printable silver pastes and is said to reduce the formation of hotspots in solar modules and to prolong panel lifespan. The composite metal contacts are also ‘self-healing’ as they are able to regain electrical continuity after cycles of complete electrical failure caused by extreme strain.