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7 May 2009


BluGlass to expand RPCVD to nitride-based solar cells

BluGlass Ltd, which was spun off from Australia’s Macquarie University in 2005, says that it intends to expand the market potential of its remote plasma chemical vapor deposition (RPCVD) manufacturing technology to thin-film solar cells incorporating group III-nitride materials. The firm currently develops and commercializes RPCVD for depositing thin films such as gallium nitride (GaN) and indium gallium nitride (InGaN) in the production of LEDs.

BluGlass says that, although there are many materials from which solar cells can be developed, group III nitride semiconductors have many advantages over current materials. This is due the alloy InGaN having a direct energy bandgap with wide tunability, giving the potential to convert almost the full spectrum of sunlight (infrared, visible and ultraviolet radiation) to electrical current. Such properties hence allow more energy from the solar spectrum to be captured efficiently by a solar cell and converted to electrical power. If successful, InGaN solar cells promise to be long lasting, relatively inexpensive and highly efficient, reckons BluGlass.

To date, solar cells have been capable of a maximum efficiency of 41.1% (and only using advanced laboratory technologies). In contrast, most commercial solar cells are retailed at efficiencies of 5-28%, due to the fact that commonly used materials have either a high or an indirect energy bandgap, limiting their potential. Research has established that InGaN solar cells could produce efficiencies of more than 50% [Jani et al. Applied Physics Letters 91, 132117-3 (2007)]. If this could be achieved in practice, then it would represent the biggest ever breakthrough in solar cell efficiency.

BluGlass says that RPCVD has advantages over existing commercial processes, including being more environmentally sensitive and having significant low cost potential. Also, being a low-temperature process, it is suited to the growth of InGaN: during the growth process, the alloy's fragile bonds crack at high temperature, leading to poor-quality material. A low-temperature process would hence allow indium-rich InGaN layers to be grown. Currently, the standard nitride growth process of metal-organic chemical vapor deposition (MOCVD) relies on extreme temperatures of over 1000ºC to achieve the active nitrogen species. In contrast, BluGlass’ process extracts the active nitrogen directly from a nitrogen plasma source, which allows low-temperature growth to be achieved.

InGaN also has superior resistance to energy radiation and high-temperature tolerance. Hence nitride solar cells could maintain high performance under extreme conditions, including space applications such as powering satellites and space probes. Furthermore, the inherent scalability of the RPCVD process (which has been demonstrated by growing GaN for LED applications) is another potential benefit of the process over existing manufacturing methods, reckons BluGlass’ CEO Giles Bourne.

Following recent research on InGaN, BluGlass aims to develop a prototype high-efficiency solar cell for industrial testing. It has already designed a solar cell structure that has been grown using MOCVD and fabricated into a device at BluGlass. This cell will be used as a benchmark for subsequent development work carried out on the RPCVD process.

While solar applications present a natural progression (as RPCVD technology is so well suited to such applications), Bourne stresses that LEDs remain the primary focus of BluGlass’ business.

See related items:

BluGlass forms Technology Council to drive commercialization

BluGlass’s plant opened by Australian Environment Minister

BluGlass to open pilot manufacturing plant in July

EMF announces multiple MOCVD orders

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