Sustainable Energy

A Xerox Machine for Super Solar Panels

Researchers at PARC are working on a way to cheaply print efficient solar cells at a large scale.

The technology giant that’s synonymous with photocopied documents has set its sights on highly efficient solar panels.

Researchers at PARC, an R&D-focused subsidiary of Xerox, say they’re developing a new digital printing process that could make it much cheaper to mass-produce concentrated solar photovoltaic systems. Such systems can dramatically increase the efficiency of solar cells by using lenses to concentrate and focus the sunlight onto small cells.

Increasing efficiency could be an effective way to bring down the cost of solar modules, whose price has already fallen dramatically during the past several years. Much of the cost of conventional silicon systems is now due to things like wiring, installation, and permitting. More efficient panels would mean we need fewer of them to produce the same amount of power—which in turn cuts the costs of hardware and installation. But concentrated photovoltaic technology has so far failed to gain traction because it’s still too expensive and bulky to compete with conventional silicon solar panels.

PARC hopes to make the technology more competitive by shrinking the components and designing a new flat-panel form factor, and by developing a relatively inexpensive manufacturing process. The new process will build on a larger effort by PARC researchers to invent a new kind of printer that can precisely deposit “inks” made of tiny semiconductor chips, called “chiplets,” by using assembly principles similar to those behind Xerox photocopiers.

So far, they have demonstrated only the ability to make small-scale devices by wiring together a few printed chiplets. But eventually the technique could allow people to design and print very large arrangements of small electrical and optical components similar to the way they would design and print a document using a Xerox printer, say the PARC researchers. They say this should make it possible to develop a new class of electronic devices made of printed arrangements of various kinds of chiplets.

The first real application could be new kind of solar power system. In August, the PARC group, along with collaborators at Sandia National Laboratories, won a grant from ARPA-E to apply the innovative printing process to build microscale arrays of photovoltaic cells on a flat panel, and the group has three years to do it (see “DOE Attempts to Jump-Start Concentrated Solar”).

In recent years, engineers have developed ways to shrink the components needed for concentrating and focusing sunlight down to the millimeter scale. Researchers at Sandia National Laboratories have developed microscale solar cells that can be paired with those concentrating elements in a flat-panel design. But the smaller the components, the more individual parts there are to assemble for a given area, and they must be arranged with extreme precision, says Patrick Maeda, a principal engineer at PARC.

The existing method for doing this, which relies on an automated system that picks up individual components and places them in target spots, is much too expensive to achieve ARPA-E’s ambitious cost objective, says Maeda. The PARC researchers say the new printing approach could lead to a high-speed manufacturing process that is orders of magnitude cheaper for building these microscale systems over large areas.

The big challenge now is to design and build a system with hundreds of chiplets wired together, says Eugene Chow, a PARC principal scientist. In three years the group must deliver an electrically functional array of solar cell chiplets. Such a “backplane” could then be combined with miniature optical components that can be made using methods commonly used to manufacture large-area optical films used in flat-panel displays.

The ARPA-E funding has pushed the group to “get more serious about industrial applications” for the chiplet printing process, says Chow. “But we still have a long way to go.”


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