News Collection

The project CPVMatch has been bringing the practical performance of high concentrating photovoltaics (HCPV) closer to theoretical limits.

The project started in May 2015 and ended in October 2018. The consortium consisted of four research institutions (Fraunhofer ISE, RSE, CEA, Tecnalia), one University (UPM), two industry partners (AZUR Space Solar Power, AIXTRON) and two SMEs (ASSE, Cycleco) and the project was coordinated by Fraunhofer ISE.

In their research the consortium addressed all topics required to manufacture highly efficient CPV modules. This included material issues, manufacturing and equipment aspects and production challenges. University and research institutes were working in close cooperation with industry partners in order to ensure fast industrial exploitation of all results within the whole value chain.

The central objective of CPVMatch was to realise HCPV solar cells and modules with the highest efficiencies, with a low environmental impact.

Wafer bonded 4j cells on Ge substrate have been manufactured. The best efficiency realised is 42.6 %. Building blocks that allow for further improvement have been demonstrated including passivated Germanium cells and top cells grown in an upright manner. Putting together these already successfully demonstrated blocks will allow for efficiencies of 45 % in short term and 46 % is possible in the future. This development was accompanied by intensive modelling which was adapted and further improved.

 Wafer with multi-junction concentrator solar cells. © Fraunhofer ISE

In the development towards a lattice matched four-junction solar cell that does not require a wafer bonding step important developments on the growth of SiGeSn by MOVPE have been realized. A new MOVPE growth chamber allowing for the growth of both group IV and III-V materials has been installed and qualified. It has been used for the growth of SiGeSn solar devices that for the first time have been grown in the same MOVPE growth chamber utilized for the III-V growth. A SiGeSn/Ge heterojunction solar cell has been manufactured that demonstrated the ability for generating a current density of 16 mA/cm² when implemented in a four-junction device (bandgap 1 eV, filtered by GaAs on top). Besides future implementation in four-junction solar cells the SiGeSn layers show great potential for usage as passivation layers for III-V solar cells.

Metalorganic vapour phase epitaxy (MOVPE) reactor. © AIXTRON

A new achromatic ‘biFresnel’ lens has been designed and manufactured called achromatic doublet on glass (ADG). The side-by-side comparison between standard SOG (silicone on glass) and ADG lens based mono modules showed almost same efficiency (29.6 % vs. 28.2 % at CSOC), despite the immaturity of the ADG technology compared to SOG. The ADG concept has proven its achromatic behaviour leading to a lower dependence of performance on temperature. Large arrays have been manufactured and modules built. In order to demonstrate the full potential of achromatic optics a module has been assembled, using four junction solar cells (with 44 – 45 % efficiency) and full glass achromatic lenses with AR coating showing a CSTC efficiency of 41.4%.

World record CPV module - 41.4% efficiency at CSTC © Fraunhofer ISE/A.Wekkeli

Array of Novel Achromatic Doublet on Glass Fresnel lenses. © IES-UPM

A compact, mirror concentrator has been designed and realized. The concept is composed by an off-axis paraboloid mirror, as primary optic and an optimized reflective secondary optics as a homogenizer. The realized concentration ratio is 980x. Several mono modules and large size modules have been manufactured. So far, only 3j cells have been used. Efficiencies of 33.3 % for mono and 30 % for large modules, at operating conditions, have been achieved. Further improvements in the module alignment and replacing the 3j cells with 4j cells pave the way to efficiencies of 40 %.

New compact mirror-based concentrator module. © ASSE

Measurement tools, for the characterisation of CPV optics and cells, were developed, introduced, and used for the characterization, within the project. In this context, CPVMatch partners were continuously supporting the standardisation activities in the IEC technical committee 82 working group 7 responsible for standards in the field of CPV.

Indoor characterization test bench METHOD. © P. Avavian/CEA 

A life cycle assessment (LCA) for CPV has been performed. The analysis covers the entire life cycle of the product. CO₂ emissions between 16 and 18 gCO₂eq/kWh were found, and further optimisation potential has been identified. The analysis of costs is challenging as the technologies are not yet to industrial-scale production. However, other benefits that CPV is offering have been identified, which at the moment cannot be directly linked to costs, as the above mentioned lower CO₂ emissions, the possibility of dual-use of the land and potential high local manufacturing content.