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Posted: September 21, 2009

IMEC unveils promising mechanically-stacked GaAs/Ge multijunction solar cell

(Nanowerk News) At the European Photovoltaic Solar Energy Conference (Hamburg, Germany), IMEC presents a mechanically-stacked GaAs/Ge multijunction solar cell. This is the first promising demonstrator of IMECís novel technology to produce mechanically stacked, high-efficiency multijunction solar cells, aiming at efficiencies above 40%.
At the top of the stack is a one-side contacted GaAs top cell that is only 4Ķm thick and that is transparent for infrared light. Its efficiency is 23.4%, which is close to the efficiency of standard GaAs cells. IMEC has succeeded in transferring this GaAs top cell onto a Ge bottom cell, creating a mechanical stack. In that stack, the Ge bottom cell is separately contacted. It has a potential efficiency of 3-3.5%, which is higher than Ge bottom cells in state-of-the-art monolithically stacked InGaP/(In)GaAs/Ge cells. Looking forward, Giovanni Flamand, team manager at IMEC, expects to show a first working triple-junction cell beginning of 2010.
This cell is a demonstrator of IMECís innovative technology to produce mechanically stacked, high-efficiency InGaP/GaAs/Ge triple-junction solar cells. This includes manufacturing world-class thin-film III-V cells and Ge bottom cells, and developing a technology to mechanically stack them. The expected conversion efficiencies are 1-2% higher than those obtained today with monolithic triple-junction solar cells (> 40% with concentrated illumination). In addition, the new cells show an enhanced spectral robustness. Stacked solar cells combine cells made from different materials to capture and converse a larger part of the light spectrum than is possible with a single material.
Dr. Jef Poortmans, IMECís Photovoltaics Program Director: ďMechanical stacks are more complex to handle and interconnect. But they definitely offer a way to increase the conversion efficiency and energy yield of high-efficiency solar cells. And they also enable an efficient way to try and use new combinations of materials. For this technology, we profit from IMECís expertise in 3D stacking, growing III-V layers, and solar cell processing.Ē
About IMEC
IMEC is a world-leading independent research center in nanoelectronics and nanotechnology. IMEC is headquartered in Leuven, Belgium, and has offices in Belgium, the Netherlands, Taiwan, US, China and Japan. Its staff of more than 1,650 people include over 550 industrial residents and guest researchers. In 2008, IMEC's revenue (P&L) was 270 million euro.
IMEC's More Moore research targets semiconductor scaling for the 22nm technology node and beyond. With its More than Moore research, IMEC invents technology for nomadic embedded systems, wireless autonomous transducer solutions, biomedical electronics, photovoltaics, organic electronics and GaN power electronics.
IMEC's research bridges the gap between the fundamental research at universities and R&D in the industry. It has unique processing and system know-how, intellectual property portfolio, state-of-the-art infrastructure, and a strong and worldwide network position. This makes IMEC a key partner for shaping the technology of the future.
IMEC is a registered trademark for the activities of IMEC International (a legal entity set up under Belgian law as a "stichting van openbaar nut"), IMEC in Belgium (IMEC vzw supported by the Flemish Government), stichting IMEC Nederland (IMEC-NL) and IMEC Taiwan Co. (IMEC-TW).
Source: IMEC
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