I have often wondered whether some of the things I am told during my visits to semiconductor vendors are misleading by accident, or whether there isn't sometimes a more deliberate attempt to keep a sensitive part of the story quiet. As a journalist, I expect to hear news and forecasts of progress in technology, techniques, and results, but I don't expect to hear about a quantum (most apropos, as you will see) leap until very close to the unveiling of that special new thing.
When I read in these pages Lee Goldberg's report of his visit to Solar Power 2007, in Long Beach, I was struck by some of the stuff he didn't write about, central to the production of electricity from the sun's energy. Lee, rightly, recognizes the incredible commercial business that lies ahead for the industry, but it seems companies are trying to keep quiet about a few things that, presumably, they think their competitors aren't supposed to know about.
Lee hinted, and others agree, that the 10% efficiency point for a photovoltaic cell is also the point at which the industry becomes viable. I couldn't disagree more. At 10% I don't have enough roof real estate to mount the number of cells I would need to power my home, let alone sell some of it back to the grid. At 20% efficiency I probably could be in line for a viable solar-powered home.
When is the industry going to get to those levels of efficiency? The common answers from the solar cell companies seems to range from five years to a blanket never.
Well, folks, that efficiency can be had today; but it has not been commercialized. Yet…
Australia is not well known for technology breakthroughs -- and the biggest development in this field does not come from there -- but The University of New South Wales, in Sydney, is the only place of further education I know of that has a School of Photovoltaic and Renewable Energy Engineering producing graduates and postgraduates who are more aware of the possibilities of future power sources than most of us could imagine to exist. They are deep into research and the School's faculty wins frequent awards for their progress.
One of those awards was a few days ago when Professor Martin Green was given the highest honor possible to a foreign expert for his contribution to China's scientific progress in renewable energy. The provincial nomination that brought him his moment of glory in the Great Hall of the People in Beijing came from a former student, Dr Zhengrong Shi, who founded the solar cell vendor Suntech-Power -- the first privately-held mainland company to be listed on the New York Stock Exchange (NYSE:STP) which had nearly $320 M in revenues for the quarter ending June 30, 2007.
Work done by UNSW and engineered at the Australian National University (ANU), in Canberra (Australia Capital Territory -- ACT) with Dr Kylie Catchpole and Dr Andrew Blakers (Head of the Photovoltaic Group in the Faculty of Engineering and Information Technology), together with a graduate researcher, have invented a process they are calling epilift where the very thin, pure, silicon wafer needed for silicon photovoltaics is grown on a solid silicon substrate and then, like a pancake, is peeled off when it is at optimal thickness. No mechanical sawing or grinding is required. And the silicon substrate can then be re-used again and again! Because the thickness can be controlled it is also expected that a semi-transparent cell might do double duty as a shade window.
It is forecast that efficiencies will rise to at least 13% and, perhaps, to 15%. Getting closer, but there is still not enough space on my roof. Dr Catchpole is also working on a silver depositing process that when heated to about 200°C causes 100 nm islands of silver to be created in the silicon -- greatly increasing the cell's ability to trap light and, therefore, increasing efficiency yet again. But it isn't getting the product cost down any.
Dr Blakers is no slouch when it comes to photovoltaic cells: he created a cell with an 18% efficiency in 1983, 19% in 1984, 20% in 1985, and 22% in 1989.
The biggest breakthrough in this field is coming, however, out of one of the only civilized parts of downtown Houston -- Rice University. The technique has been known for some time but the ability to successfully implement it has not.
It has been shown that instead of using silicon, quantum dots made with cadmium selenide are really good at converting photon energy into electrons and holes. This is particularly true of tetrapod (four-legged) quantum dots which have been very difficult to engineer.
An assistant professor at Rice, Michael Wong, together with a couple of graduate students has developed a recipe for creating tetrapods with a 90% success rate -- more than three times higher than previous work. The breakthrough was achieved by the simple expedient of replacing a rather nasty chemical (plenty of those in and around Houston), one of the alkylphosphonic acids, with the benign, odorless, cetyltrimethylammonium bromide (CTAB) -- an extremely low-cost compound that you will probably find on the label of your anti-bacterial hair shampoo.
Results of the technology when it gets commercialized for solar purposes? Much smaller cells for the same output as silicon (i.e. much, much higher efficiency), at much lower prices. Timescale? 3M was one of the sponsors of the research…
The chemistry will also allow for the development of a range of medical test equipment using the tetrapod serendipity of how it can manipulate light and its spectrum.
So why is the industry still messing with inefficient, costly silicon when our solar future will come out of a bottle?
