In the quest for greater dependence on renewable energy, looking at methods for improving existing technology is as worthwhile a pursuit as seeking to develop that “eureka” solution. Of course, everyone would like to find that holy grail, but if we’re talking about moving towards a society that embraces renewable energy, in all its form and splendor, as its primary power source, then every refinement, every tweak, every reimagining brings us one step closer to the tipping point.

While some of these proposed improvements border on the scale of Industrial Revolution heavy engineering, others are very small indeed. New work by a team of scientists in Eindhoven, the Netherlands, focuses on improving solar cells right down at the single-molecule scale. As with most things, one strategy for improving the performance of silicon-based solar cells is to improve their efficiency, achieved by reducing charge loss at their surface. Being able to stop up these leaks (or charge recombinations) successfully would mean that thinner silicon wafers could be used in production, reducing the amount of material used per unit. Aluminum oxide coatings have already been demonstrated as an effective passivating layer for silicon solar cells, but industrial adoption of passivating coatings has been hampered by lack of a technique capable of laying down the coatings at a speed consistent with manufacturing throughput. What Paul Poodt and his team have come up with as a solution is to adopt a variant of a technique called atomic layer deposition. ALD is a derivative of chemical vapor deposition, much used in CMOS semiconductor manufacturing since it’s capable of producing conformal single-molecule coatings on substrates. It’s a very precise but somewhat slow technique, as it involves obtaining the coating by initiating two half-reactions with purge steps between each reaction. However, the team in Eindhoven have literally taken ALD into a new dimension by separating the half-reactions spatially rather than temporally. By adopting a conveyor belt approach they can move the substrate through the reaction chamber and have the reactions running simultaneously, speeding up the process to rates acceptable to industrial throughput.

So far so good for passivating solar cells, but one of ALD’s great strengths is its versatility, and this technique could be good for applications in lighting and display technology, flexible electronics, or any process where encapsulation or barrier/buffer layers might be needed. Poodt and his team envisage this as being just one step along the road to new manufacturing tools for next generation electronics.

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P. Poodt et al. Adv. Mater. ; DOI: 10.1002/adma.201000766