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Existing CPV technology markets are not compliant with a standard configuration. Concentrations vary from several suns to more than 1000 suns and the optical technology used could be very different. Nowadays, the market trends are moving toward more and more compact optical systems in order to exploit the Light Emitting Diode (LED) like approach. The aim is to increase the optical efficiency by using an ultra-short focal distance and to improve thermal management. Moreover the efficiency to weight ratio is increasing and the solar cell size becomes sub-millimetric. With these conditions, more stringent mechanical tolerances are essential to ensure an optimum optical alignment between cells and optics. A new process of micro-concentrator manufacturing is developed in this work. This process enables manufacturing and auto-alignment of Primary Optical Elements (POE) with Secondary Optical Elements (SOE) and solar cells with respect to certain mechanical tolerances. A 1000X micro-concentrator is manufactured ...

As the SOPHIA round robin aims for comparing different power rating methods, all partners agreed to use the same measurement guideline. This guideline considers the module alignment, the data requirement and the duration of data collection. Three methods to calculate the rated power from measurement data based on regression, averaging or translation are already evaluated using data of the first four partners. Initial results show maximum deviations in the rated power output between the test labs of less than about four per cent for the investigated rating methods.

Starting on June 2011, NGCPV has been the first coordinated project between the European Commission and Japanese NEDO in order to advance in the science and technology of concentrator photovoltaics (CPV). Research has covered all relevant areas in CPV, from solar cells to complete systems, including multijunction solar cells, novel solar cell concepts utilizing nanostructures, advanced optics and modules, thermal management, reliability and modeling at all the stages of the CPV chain, rating and round robin schemes and the development of characterization tools for cells, modules and systems (outdoor and indoor). Ending in November 2014, the NGCPV project has attained some remarkable results, such as the manufacturing of a 44.4% world record efficiency triple junction solar cell (by Sharp Corp.) and the development of a 15 kW CPV system (by Daido, BSQ and UPM) with a DC efficiency of 28% under CSOC, which is the highest reported in the world at system level. In this paper we summarize these and other relevant results concerning project activities such as the investigation of novel buffers for growing III-V materials on silicon, novel ~1eV materials for manufacturing quad-junction solar cells, the development of accurate models to forecast the electricity production in CPV plants and novel advanced optical designs for CPV modules, among others.

In this paper, we present an improved 3D distributed model that considers real operation regimes in a tunnel junction. This advanced method is able to accurately simulate the high concentrations at which the current in the solar cell surpasses the peak current of the tunnel junction. Simulations of dual-junction solar cells were carried out with different light profiles and including chromatic aberration to show the capabilities of the model. Such simulations show that, under some circumstances, the solar cell short circuit current may be slightly higher than the tunnel junction peak current without showing the characteristic dip in the J-V curve. This behavior is caused by the lateral current spreading towards the dark regions, which occurs through the anode region of the tunnel junction.

This paper presents research efforts conducted at the IES-UPM in the development of an accurate, physically-based solar cell model using the generalpurpose ATLASR device simulator by Silvaco. Unlike solar cell models based on a combination of discrete electrical components, this novel model extracts the electrical characteristics of a solar cell based on virtual fabrication of its physical structure, allowing for direct manipulation of materials, dimensions, and dopings. As single junction solar cells simulation was yet achieved, the next step towards advanced simulations of multi-junction cells (MJC) is the simulation of the tunnel diodes, which interconnect the subcells in a monolithic MJC. The first results simulating a Dual- Junction (DJ) GaInP/GaAs solar cells are shown in this paper including a complete Tunnel Junction (TJ) model and the resonant cavity effect occurring in the bottom cell. Simulation and experimental results were compared in order to test the accuracy of the models employed.

Characterization is a key process in attaining high efficiency in the state-of-the-art multi-junction solar cells. This work will summarize our efforts in using eletroluminescence for characterising multijunction solar cells. This study will present the possibilities of electroluminescence (EL) spectroscopy as a fast and simple characterization technique which is able to provide extensive information about the solar cell’s performance. Finally, four of the applications of this technique will be presented: band gap estimation, barrier effect for minority carriers, information on the thermal performance of encapsulated devices and determination of the shunt resistance of each cell in a dual junction device.