Solar Server interview with Dave Epstein, CEO, SolVoltaics

by Solar Server International Correspondent Christian Roselund
April 14th, 2013

Dave Epstein
Dave Epstein

Solar Server: With so many approaches out there to improve PV efficiencies, what are the main compelling distinctions of Sol Voltaics' technology?

Dave Epstein: Sol Voltaics is producing an active layer ink called Solink™ that goes on top of silicon solar panels.  This ink contains tiny nanowires – just 1 to 2 microns long made of Gallium Arsenide.  These wires act as miniature solar cells.  Put billions of them together and you create a lot of energy. 

So the first difference is that this active layer doesn’t just improve the silicon panel below, it adds to the power generated.  So the efficiency of the final module is a combination of the efficiency of our active ink layer and that of the silicon panel underneath, which converts the light Solink™ doesn’t absorb.

The next distinction is that we use Gallium Arsenide (GaAs), the most efficient material in common use in solar panels.  This is why it adds to the power – it converts a different spectrum of light into power, allowing the final output to be greater that even the absolute best silicon panels in the market. 

Finally, we produce these wires very cheaply – cost competitive with the silicon.  This is done by a very innovative method called Aerotaxy™, developed by our founder and world renowned nanotechnology professor Lars Samuelson of Lund University.  Aerotaxy produces nanowires orders of magnitude more cheaply than the conventional method. 

Put these together, and you have the reason we are such an exciting company.


Solar Server: Your promotional materials state that Sol Voltaics can bring about a 25% improvement in efficiencies. Can you give a brief overview of how your technology can achieve that level of efficiency gain?

Dave Epstein: There is a fascinating phenomenon that occurs when light passes over nanowires of the dimensions we produce. They act as “antennas” or wave guides for light. What this means is that those wires attract more light than what one might expect their tiny dimensions to capture.

Indium phosphide nanowire array (Image courtesy Solvoltaics)
Indium phosphide nanowire array (Image courtesy Solvoltaics)

We call this non-mechanical, non-optical, wave effect: Wave Concentrated Photovoltaics, or WCPV. This means that for a sparse array of these wires, say 10-20% coverage, we can capture a large majority of the light that falls on the entire area. 

To prove this, we joined an EU funded project with Lund University and others and created a nanowire only cell made from indium phosphide which has a champion cell (as a complete planer layer) conversion efficiency of 22%. With just 12% coverage of the nanowires, we showed an impressive 13.8% efficiency which was certified by Fraunhofer Institute.

So we captured 60% of the light with just 12% coverage - a clear indication that concentration is occurring. So, using GaAs and WCPV, the conversion efficiency becomes very high while just covering part of the panel with nanowires. 


Solar Server: The PV industry has been described as increasingly commoditized, with manufacturers struggling to beat each other to lower cost per watt. Can you explain to our readers the business case for spending more on equipment to achieve higher efficiencies?

Dave Epstein: Module manufacturers are struggling because there are just too many suppliers. The good news is that the cost has dropped, which expands the geographies where PV is competitive with utility energy. Solid growth reached about 66% growth in China and more than 70% increase in installations in the US.

The bad news for the suppliers is that all the cost has been squeezed out of the modules prices and there is little more to be had in cost cutting. The way to improve the economics, then, is to improve the product so that customers might pay a bit more, but they will get outsized benefits for a stable or increase in price.

That is what efficiency does. A 200W panel that becomes a 250W panel requires fewer panels for the same power, or more power for the same number of panels. Thus, the installed cost per Watt can be less with the same or even a bit higher priced modules.

This demand for higher performing modules is evident when comparing the price of panels below 15% averaging around 65 cents per Watt peak while 18% to 24% modules average 94 cents today. Clearly, customers want efficiency and they are willing to pay for it.

Don’t get me wrong, there will be a market for these lower efficiency panels, but they will sell for rock bottom prices – even 40 cents or below.

The healthy market will be above 18% and at prices of 70 cents or more. That is what people want, and that is the region where Sol Voltaics will deliver – 20 to 30% efficient panels at 70 to 95 cents per Watt. 


Solar Server: I notice that Sol Voltaics' team includes some big names in science and the PV industry. Can you talk about how the team came together?

Dave Epstein: Professor Lars Samuelson of Lund University is our founder and our Chief Scientific Officer. He is an incredible technologist, scientist and visionary. He founded the Nanometer Structure Consortium at the university now sporting some 200 scientists and researchers which produces some of the world’s most advanced research in the field.

Sol Voltaics was founded with the inventors of Aerotaxy and have since attracted scientists and executives from all over the world to bring this technology to the market. We have people from IBM research, Applied Materials, Agilent, Heliovolt, Evergreen Solar and more.

Not only the best research talent, but we bring high volume industry talent as well. Sol Voltaics isn’t just advancing the state-of-the-art; we are bringing to market materials that can have a major impact on the cost/performance of clean energy. 


Solar Server: Can you tell use more about your Solink product that is scheduled for release in 2015?

Dave Epstein: Solink is designed for compatibility with existing production lines and industry practices. We are not panel manufacturers, but rather, we will ship Solink to them as well as provide techniques for adding Solink into their crystalline silicon or thin film production lines, with a few straightforward and inexpensive process steps at the end of their current production process.

We will be demonstrating high efficiencies this year and next, and partnering with both module manufacturers and equipment manufacturers. Solink will be in pilot production in 2015 with module manufacturer partners.

We are a material manufacturer producing an ink and partnering with the module producers to make their panels more attractive, command higher prices and allow their customers to make more money while selling their installed power plants for less money per Watt.

We are very excited about the prospects for Solink and Sol Voltaics. Thank you for the opportunity to speak with you, Christian, and with Solar Server.