INTERSOLAR, San Francisco (USA) – July 3, 2013 – At next week’s Intersolar conference in San Francisco, imomec, imec’s associated lab at the Hasselt University, and Solliance, the European R&D consortium that focuses on thin-film photovoltaic solar energy (PV), will present a CZTSe (Cu₂ZnSnSe₄)-based solar cell with 9.7 percent efficiency (1x1cm², AM1.5G)*. This promising result is an important step bringing the solar industry closer to a sustainable alternative for the highest efficiency thin-film solar cells in production, based on CIGS (Cu(In,Ga)(S,Se)₂).

CZTSe is an emerging alternative solar cell absorber in thin-film solar cells, similar to CZTS (Cu₂ZnSnS₄). Unlike CIGS, CZTS and CZTSe do not suffer from abundancy issues. At 1.5-1.6eV for CZTS, and 0.9eV for CZTSe, their bandgaps make a combined material system ideal for a multi-junction, thin-film solar cell that rivals the efficiency of CIGS cells (about 20 percent). Imomec, imec and Solliance have defined a path towards further improving the layers and cell structures of CZTSe and CZTS absorbers aiming at developing a multi junction CZTS/CZTSe solar cell with 20 percent cell efficiency. The presented CZTSe solar cell is an important step forward to reach this goal.

Imec/imomec fabricated the CZTSe layers by sputtering Cu, Zn and Sn metal layers on a Molybdenum-on-glass substrate and subsequent annealing in an H₂Se containing atmosphere, achieving 9.7 percent efficiency. The resulting polycrystalline absorber layers are only 1µm thick, with a typical grain size of about 1µm. The samples were then processed at Helmholtz Zentrum Berlin into solar cells using a standard process flow for thin film solar cells and finished with a metal grid and anti-reflective coating at imec. The highest efficiency obtained on a 1x1cm² cell was 9.7 percent, with a maximum short circuit current of 38.9mA/cm², an open circuit voltage of 0.41V and a fill factor of 61 percent.

“This is a big win for us. We’ve been working toward this milestone since 2011 when we first started our research on alternative materials for thin-film photovoltaics at imec/imomec,” said Marc Meuris, program manager Solliance of the alternative thin-film PV program. “Our efficiencies are the highest in Europe and approaching the world record for this type of thin-film solar cells, and we look forward to further advancing R&D to help bringing to market sustainable energy sources.”

The sputtering of the Cu, Zn, Sn layers was performed at Flamac (Gent), and the international glass manufacturer AGC delivered Molybdenum-on- glass substrates. Imec’s thin-film solar cell activities at imomec (imec’s associated laboratory at the university of Hasselt) are integrated in the Solliance cross-border collaboration platform, and the research was partially supported by the Flemish ‘Strategisch Initiatief Materialen’ (SIM) SoPPoM program.

* Certification expected in October 2013.

Thin-film CZTSe solar cell achieving 9.7% efficiency

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About imec
Imec performs world-leading research in nanoelectronics. Imec leverages its scientific knowledge with the innovative power of its global partnerships in ICT, healthcare and energy. Imec delivers industry-relevant technology solutions. In a unique high-tech environment, its international top talent is committed to providing the building blocks for a better life in a sustainable society. Imec is headquartered in Leuven, Belgium, and has offices in Belgium, the Netherlands, Taiwan, US, China, India and Japan. Its staff of more than 2,000 people includes more than 650 industrial residents and guest researchers. In 2012, imec's revenue (P&L) totaled 320 million euro. Further information on imec can be found at www.imec.be.

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 Belgium (IMEC vzw supported by the Flemish Government), imec the Netherlands (Stichting IMEC Nederland, part of Holst Centre which is supported by the Dutch Government), imec Taiwan (IMEC Taiwan Co.) and imec China (IMEC Microelectronics (Shanghai) Co. Ltd.) and imec India (Imec India Private Limited).

About Imomec
Imomec is the associated lab of imec at the Hasselt University (Belgium). Together with imo, the research institute of Hasselt University, it forms the Institute of Materials Research, imo-imomec. The core competences of imo-imomec are the development and characterization of new material systems with potential use in microelectronics, bioelectronics and nanotechnology. Particular attention is paid to novel organic and inorganic photovoltaic materials, advanced electro-optical and morphological characterization and reliability of novel generation solar cells including CZTSe, OPV, hybrid solar cells and printable solar cells. The lab counts more than120 people. Further information on imo-imomec can be found on www.uhasselt.be/IMO.

Contact:
imec:
Katrien Marent
Director External Communications
M: +32 474 30 28 66
katrien.marent@imec.be

Solliance:
Hein Willems
Director
T: +31 88 515 4472
M: +31 225 200 99