This report briefly describes the research activities carried out by RSE in the 2017 Annual Implementation Plan in the Concentrator Solar Photovoltaic (CPV) Project, under the Electricity System Research (RdS) 2015-2017 Program Agreement.

The aim of the project was to help reduce the cost of CPV technology to make it more competitive with other energy sources and to overcome the technological barriers that still limit its full market penetration.

RSE’s research, also carried out in collaboration with national and international research institutes and operators, has enabled the development and implementation of innovative technological solutions at all stages of the CPV technology chain, contributing in particular to: 1) the identification of new materials and manufacturing processes that are more economical for the growth of CPV cells; 2) reducing the manufacturing costs of CPV modules by producing modules with more compact dimensions and that can operate at higher solar concentration factors; 3) analysing the causes that reduce the reliability of modules, and thus 4) reducing the costs of implementing, operating and maintaining CPV generation systems.

During 2017, to enable the production of low-cost InGaP/InGaAs/SiGeSn/Gemonolithic 4-junction CPV cells, a number of important intermediate goals were pursued and achieved, such as in particular 1) optimizing the growth of InGaP and InGaAs sub-cells, by reducing their deposition temperature by about 100 °C (compared with the growth temperature in triple-junction cells), so as to facilitate their better integration into the quadruple-junction cell, 2) reducing cross-contamination between group IV elements (Si, Ge, and Sn) and III-V compounds (Ga, In, P, and As) in order to make SiGeSn, InGaAs and InGaP ternaries in the same MOCVD growth chamber, suitably modified, achieving a result that had never been reported in the literature, 3) developing post-growth processes of miniaturized (2.4×2.4 mm2) multi-junction cells at high concentration (up to 1000X), and 4) developing innovative optics and nanostructured anti-reflective coatings for CPV cells.

In addition, a prototype of a compact CPV module was characterized, the innovative MPPT algorithm developed by RSE for inverters connected to CPV systems was validated, and the accuracy of the low-cost solar orientation sensor that can be integrated into the CPV module was verified.

Finally, the activity of collecting and managing national data on direct solar irradiance and spectral irradiance from different national sites was continued in collaboration with the members of the relevant consortium. In the course of this activity, the use of the innovative SSIM direct solar radiation meter was optimized and the procedure for verifying the measured spectral data was refined.