FREE subscription
Subscribe for free to receive each issue of Semiconductor Today magazine and weekly news brief.


9 October 2008


QD PV maker Solterra acquired by mineral company

Last week, publicly traded mineral exploration company Hague Corp of Manitoba, Canada signed a binding letter of intent to purchase the assets of Solterra Renewable Technologies Inc of Scottsdale, AZ, USA, requiring Hague to provide funds totaling $5m within 60 days of signing a final asset purchase agreement.

Solterra is developing a thin-film quantum dot (QD) solar cell that, it claims, can result in lower cost, higher efficiency, and broader spectral performance compared to traditional cells.

Solterra reckons that its QD solar cell can achieve a dramatically lower manufacturing cost per watt partly because it will manufacture quantum dots using a patent-pending process developed by quantum dot expert Dr Michael Wong and his team at Rice University (from which Solterra was spun off). The process results in the production of high-quality tetrapod quantum dots at a cost saving in excess of 95% compared to existing production processes, it is claimed. In addition to cost savings compared to other QD production methods, photovoltaic quantum dots have the potential to achieve a solar energy conversion efficiency of more than 90% (about three times the theoretical limit of silicon-based solar cells). They can also be tuned to deliver either high voltage or high current (difficult with conventional silicon solar cells) and be placed behind a protective shell (ensuring greater longevity and a greater return on investment for end users).

Solterra has also just concluded a worldwide exclusive license with the William Marsh Rice University for intellectual property that includes the ‘Synthesis of Uniform Nanoparticle Shapes with High Selectivity’. The licensing agreement's field of use broadly covers the manufacture and sale of photovoltaic cells and the manufacture and sales of quantum dots for electronic and medical applications.

Rice’s new chemical method for making low-cost, four-legged cadmium selenide (CdSe) quantum dots, which previous research has shown to be particularly effective at converting sunlight into electricity, removes a major barrier in developing QD-based photovoltaics as an alternative to the conventional, more expensive silicon-based solar cells, the firm claims.

The Rice process produces same-sized particles, in which more than 90% are tetrapods; previously, even in the best recipe, less than 50% of the prepared particles were tetrapods. Furthermore, the process uses much cheaper raw materials and fewer purification steps, cutting production cost by 80% or more. the improvement in tetrapod manufacture is provided by a positively charged molecule called cetyltrimethylammonium bromide which, apart from being found in some shampoos, is also 100 times cheaper than alkylphosphonic acids and is far safer, further simplifying the manufacturing process.

“The lack of low-cost, high-quality tetrapods of the cadmium selenide kind has been a major roadblock in developing tetrapod-based solar cell devices,” says Solterra’s CEO & president Stephen B. Squires. “With this breakthrough technology, that is no longer the case,” he adds. “We are now positioned to revolutionize the solar panel industry in offering the most cost-effective and efficient panels ever produced at a time that they are more in demand than ever before.”

In addition to PV applications, low-cost high-quality quantum dots are thought to be enablers for other emerging technologies, including high-performance QD-based lasers, color displays, solid-state lighting, bioimaging, quantum computers and solar/hydrogen generation, says Solterra.

Solterra is scheduled to begin scale up of the technology in early November, with commercial production expected to start in second-half 2009.

Search: Thin-film quantum dot solar cell CdSe