DuPont’s PV mission: Lower silver, lower costs

DuPont’s Peter Brenner speaks with about lowering the silver content of PV modules, via less metallization paste, lower-silver pastes, and silver substitutes. While this sounds like a pure materials consideration, some options will change the firing equipment as well.

October 4, 2011 — DuPont Microcircuit Materials (MCM) introduced its Solamet PV51M photovoltaic metallization paste, a new tabbing material used in solar cell manufacturing, in early September. The paste enables solar module makers to use up to 15% less material, an important consideration given the rising price of silver. DuPont MCM?s roadmap has 2 key points: conversion efficiency of crystalline silicon (c-Si) solar cells beyond 20% by 2012, and lower costs for photovoltaic generated energy.

Also read: C-Si at 20% by 2012: DuPont adds to Solamet portfolio and roadmap

Peter Brenner, global marketing manager, photovoltaics, DuPont MCM, spoke with about DuPont?s new lower-silver Solamet metallization pastes. To achieve strong electrical performance with reduced silver content, the tabbing material needs to have good solderability (sufficient metal laydown) and good adhesion (which comes from very good frit properties), and may also need good conductivity.  

There are three ways in which silver content can be reduced: 1) reduce the silver content in absolute terms, 2) replace some of the silver content, or 3) reduce the metallization laydown on the cell surface. It?s very difficult to replace silver, said Brenner. One could change the amount of densification during firing (which changes the conductivity), but this technique is fairly limited with today?s available materials. Brenner explained that one could enable the silver and frit materials to better interact together so that resistive interfaces are not created.

If silver is replaced with copper, as some companies are trying to do, noted Brenner, PV assemblers would have to process copper in an inert atmosphere to get the desired resistivity by preventing oxidation. This material substitution would therefore change the PV manufacturing industry?s standard firing process to a nitrogen-fired process. ?That?s something that some of the market will consider,? explained Brenner, ?but I don?t believe all of the market will.?  

Brenner completes the podcast interview with a discussion that looks ahead to future R&D activities that will be needed to continue the company?s mission to reduce the PV industry?s dependence on silver metals.

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