This month’s roundup of leading solar innovations and breakthroughs in solar technology highlights two innovations at established solar equipment and module manufacturers that have real near-term potential to boost sunlight conversion efficiencies for crystalline solar cells – with albeit incremental gains. Also explored is a new record efficiency for an organic PV cell.
Merlin works his crystalline magic
Developer: GT Advanced Technologies
How it works: PV manufacturing equipment supplier GT Advanced Technologies in mid-March announced a new “flexible grid” metallization and interconnect technology targeted at solar cell producers. Marketed under the name “Merlin,” the production line add-on can be integrated into existing solar cell manufacturing lines, enabling producers to replace the traditional three silver bus bars on solar cells with thinner grid fingers. This produces less shading on a solar cell – meaning that more sunlight can be absorbed by the active crystalline-silicon semiconductor material and converted into electricity.
What it promises: According to GT, the manufacturing technology has the potential to cut expensive silicon paste used in the production of crystalline solar cells by up to 80 percent. It also can eliminate the need for cell stringing and tabbing machines used to produce modules – further reducing manufacturing costs. Eliminating shading has the potential to improve the efficiency of conventional crystalline PV cells. The New Hampshire-based company claims that modules made from cells relying on its Merlin technology will be more reliable and durable because the new flexible grid structure is more resistant to cell cracking.
Commercial arrival: In an investor presentation on the technology, GT said a pilot manufacturing line equipped with Merlin went online in the second half of last year. It expects to receive certification for its first Merlin-equipped commercial manufacturing line in the second half of this year at an undisclosed location, with commercial activity commencing in 2015. Given GT’s long track record of introducing new PV manufacturing technologies for conventional crystalline silicon cells, Merlin’s chances for commercial magic are good.
Back-contact solar cells
Developers: Trina Solar Ltd. and the Australian National University (ANU)
How it works: Researchers from Chinese crystalline silicon producer Trina Solar and ANU’s Centre for Sustainable Energy Systems have developed a so-called interdigitated back-contact (IBC) silicon solar cell capable of converting an impressive 24.4 percent of sunlight into electricity. IBC cells are a type of rear-contact solar cell that achieves higher efficiency by putting both contacts on the back of the cell, thus eliminating shading.
What it promises: If successfully transferred from the laboratory into commercial production, this could mean that a larger percentage of higher-efficiency solar cells will become available – since Trina is one of the world’s largest PV manufacturers.
Commercial arrival: Trina says it is developing a commercial version of its IBC cell in addition to a new module made of these cells. A 22-percent efficient IBC cell from Trina already is available in commercial modules. Trina’s press release on the innovation did not predict the precise market launch for the higher-efficiency version. It stated, however, “Though it is currently in laboratory scale, the new solar cell will soon be ready for industrialized mass production.”
Record-efficiency organic PV
Developers: VTT Technical Research Centre of Finland, IMEC International, Fraunhofer ISE, Imperial College, Corning SAS and others
How it works: Funded by a grant from the European Union, Belgian research institute IMEC International in March presented its laboratory-scale organic solar cell with a sunlight conversion efficiency of 8.4 percent – a record for this type of solar cell. IMEC achieved the record efficiency by stacking three layers of active semiconductor materials that boosted the potential sunlight absorption spectrum. IMEC’s approach does not use fullerenes, which are the most common acceptor material in organic PV cells – which, however, aren’t common at all.
What it promises: IMEC’s laboratory achievement is a signal that perhaps organic PV cells shouldn’t be completely ignored in the wake of several commercial failures in recent years – which were in part the result of the technology’s disappointing, low single-digit efficiencies. IMEC is a member of the EU-funded ArtESun collaborative effort to develop high efficiency organic solar cells capable of converting more than 15 percent of sunlight into electricity, along with roll-to-roll manufacturing equipment for this flexible solar cell.
Commercial arrival: Although an impressive collection of research institutes and companies are collaborating on this project, the reality is that organic PV cells remain far away from commercial relevance – even if very limited commercial sales of such cells already have occurred.
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