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This paper summarizes the current status of the ALCHEMI project, a European collaborative undertaking under the Solar-Era.Net co-fund scheme. The project’s aim is to develop novel, low cost, HCPV modules that operate at ∼1000 suns, and demonstrate a DC module efficiency of >37% under Concentrator Standard Test Conditions (CSTC), and a manufacturing process that will achieve costs

The development of a high quality 1eV material is one of the most import challenges in high efficiency solar cells development. The GaInP/GaInAs/1eV/Ge structure attained one of the highest solar cell efficiency, 44.0%. The dilute nitride GaNSbAs has attracted a considerable interest, since this alloy can be grown lattice-matched to GaAs with a bandgap of 1eV. However, It is well-known that N incorporation in dilute nitrides is associated with the generation of structural defects and as a result, the degradation of the optical properties. Thermal annealing is the most common procedure to improve the dilute nitrides response. In order to have a deeper understanding of the GaNSbAs layer behaviour, the effects of ex-situ annealing in N-atmosphere and in-situ annealing in As-atmosphere, have been investigated. Samples have been analysed for the first time by cathodoluminescence (CL), being this technique a good method for getting direct information in a simple, fast and non-destructive way about compositional gradients. It has been supported by scanning transmission electron microscopy (STEM) and energy dispersive spectroscopy (EDS)., Póster, Ministerio de Economía, Industria y Competitividad (Project ENE2014-56069-C4-4-R)

31st European Photovoltaic Solar Energy Conference and Exhibition; 1439-1443, In this work we present our latest results and analysis of a 10 MeV proton irradiation experiment performed on III-V solar cells. A set of representative devices were irradiated for different fluences, including latticematched GaInP/GaInAs/Ge triple junction, GaInP/Ge double junction, and GaAs and Ge single junction solar cells. The methodology applied included the irradiation of two devices of each type; for a better control of the measurements, non-irradiated devices with the same characteristics of those irradiated were used as reference. The devices were monitored before and after each exposure by in-situ characterization of the electrical response under dark and under illumination using a solar simulator connected to the irradiation chamber through a borosilicate glass window. Ex-situ characterization techniques included dark and 1 sun AM0 illumination I-V curve and external quantum efficiency measurements. Furthermore, results of the numerical simulation of devices with D-AMPS-1D code are presented in order to give a physical interpretation of the results. DLTS spectroscopy preliminary results for single junction GaAs cells are also presented.

Evaluating the reliability, warranty period, and power degradation of high concentration solar cells is crucial to introducing this new technology to the market. The reliability of high concentration GaAs solar cells, as measured in temperature accelerated life tests, is described in this paper. GaAs cells were tested under high thermal accelerated conditions that emulated operation under 700 or 1050 suns over a period exceeding 10 000 h. Progressive power degradation was observed, although no catastrophic failures occurred. An Arrhenius activation energy of 1.02 eV was determined from these tests. The solar cell reliability [R(t)] under working conditions of 65°C was evaluated for different failure limits (1–10% power loss). From this reliability function, the mean time to failure and the warranty time were evaluated. Solar cell temperature appeared to be the primary determinant of reliability and warranty period, with concentration being the secondary determinant. A 30-year warranty for these 1 mm2-sized GaAs cells (manufactured according to a light emitting diode-like approach) may be offered for both cell concentrations (700 and 1050 suns) if the solar cell is operated at a working temperature of 65°C.

25th European Photovoltaic Solar Energy Conference and Exhibition / 5th World Conference on Photovoltaic Energy Conversion, 6-10 September 2010, Valencia, Spain; 152-155, After the successful implementation of a record performing dual-junction solar cell at ultra high concentration, in this paper we present the optimization of key aspects in the transition to a triple-junction device, namely the heteronucleation of III-V structures onto germanium substrates. This optimization is based on in-situ RAS measurements during the MOVPE growth of the triple-junction solar cell structure and subsequent AFM analysis. The correlation between RAS and AFM allows detecting which RAS features correlate with good morphology and low RMS roughness. TEM analysis confirms that the quality of the triple-junction structures grown is good, revealing no trace of antiphase disorder, and showing flat, sharp and clear interfaces. Triple-junction solar cells manufactured on these structures have shown a peak efficiency of 36.2% at 700X, maintaining an efficiency over 35% from 300 to 1200 suns.