The objective of this JRP is to develop traceable metrological infrastructure in support of the rapid advances made on multi-junction solar cells that are based on III-V materials. The work program is aiming at developing techniques and methodologies to enable traceable and accurate characterization of structural, optical, electrical, optoelectronic and thermionic properties of III-V material based MJSC, from the macro to nanoscale, in order to enhance efficiency of present devices and enable the production of next generation solar cells.

The JRP addresses in detail the following scientific and technical objectives:

• To develop methods to accurately measure electrical transport properties of III-V complex heterostructures: band-gap, work function, dopant distribution, photocurrent, carrier density, diffusion length, doping dependent minority carrier lifetime, absorption coefficients and series-resistances. Accurate measurements of these physical parameters are of particular importance to deeply understand the electrical transport phenomena in these heterostructures;
• To characterize composition, thickness, structural and optical properties of III-V material in order to highlight the effect of defects concentration, microstructure and interfaces on the recombination mechanisms of charge carriers;
• To measure carrier transport between interfaces in MJSC and to characterize narrow tunnel-junction properties;
• To develop reliable tools and workflows to measure size dependent electronic structures of nanostructured semiconductor quantum dots;
• To measure thermoelectric properties of III-V material and thermal transport across interfaces;
• To develop traceable and reliable calibration methods, and standards for determining device efficiency, linearity, temperature dependence and spectral responsivity of MJSC devices.

Expected results and potential impact

There are two strategies to reduce the levelized costs of electricity from photovoltaics: the first one tends to reduce the system cost by increasing the module efficiency, which also provides the advantage of smaller systems and reduction in land area required, while the second one tends to decrease the modules cost with economies of scale in manufacturing or by using less or cheaper materials.

This JRP will focus on the first strategy by developing the metrological tools required to improve the efficiency of existing triple-junction solar cells to 50%. The project will also explore potential new cell structures to further improve efficiency and investigate the second strategy with the possibility to manufacture the cells on silicon; a substrate that is both cheaper and available in larger wafers. The project will particularly provide primary standard calibration of MJSC, a metrological infrastructure lacking at present in Europe and required by all end-users for CPV.

Specific deliverables of the JRP will be technical standard documents dealing with best practices in connection with several important topics, which are already under standardization process of ISO/IEC committees.

The proposed research will help to create impact by developing reliable and traceable measurement techniques and standards for III-V MJSC devices. The development of standard materials and procedures will help the transfer of metrology solutions between R&D laboratories and fabrication centres, thereby increasing the extent of cooperation, and adding metrological traceability to established research techniques. Moreover, success in this area will support the further development of nano-engineering and other advanced techniques, creating new opportunities to improve materials used for widespread applications and particularly renewable energies.

Improved materials metrology for III-V materials combination will also impact on a variety of other sectors. III-V technologies are used in many major lifestyle-influencing technologies such as displays and lightning (light emitting diodes), communication (diode lasers, power amplifier) or optical data storage (lasers for DVD, Blu-ray).

Updates on the project can be found here

The research within this EURAMET joint research project receives funding from the European Community's Seventh Framework Programme, ERA-NET Plus, under Grant Agreement No. 217257.