Performance and failure analysis of concentrator solar cells after intensive stressing with thermal, electrical, and combined load

Abstract

In this work, we investigated the impact of intensive heat loads on concentrator solar cells assemblies. As test samples, we employed lattice-matched and lattice-mismatched triple-junction solar cells made of GaInP/GaInAs/Ge. The thermal loads were induced by different manners. We used drying cabinets, external power supplies, and a combination of both to achieve maximum test temperatures of 180 °C. For the performance analysis, we utilized flash light solar simulators and an electroluminescence (EL) imaging tool. Our experiments revealed a significant difference depending on the applied manner of heating. The highest impact was observed for the pure heat treatment in drying cabinets. This was particularly visible in the spatial EL images, but also in the IV curves. In contrast, running the concentrator solar cells as forward-biased diodes using an external current supply of 2000 mA, which corresponds to 2000 suns, did not lead to any significant changes in EL and IV curves. However, deformation of the front metallization was observed. In conclusion, pure heat treatment can be considered as a cost-efficient alternative to pinpoint weak points in solar cell receivers

Towards miniaturization of concentrated photovoltaics (CPV): impact on fabrication, performance and robustness of solar cells

“…Whereas the effect of cell size on PMPP is not so clear than for PSSAT, microcells and larger cells have shown very good robustness under ASSAT. The difference between PSSAT and ASSAT can be explained by more aggressive stress conditions for thermal storage only, as previously reported by Eltermann et al, or by the thermal step at 230 °C required for cells mounting process used for ASSAT that may have slightly modified the cells [7].…”

“…Whereas no catastrophic failure was observed, higher performance changes occurred in the PSSAT with a minimum PMMP/PMMP0 of 0.825 at the end of the test (up to 185 °C). Similarly, Eltermann et al have shown that thermal storage only, compared to thermal storage coupled with current injection and current injection only, led to the most severe degradation of the CPV cells [7]. However, using current injection in ageing tests is often considered as a correct stressing method by the CPV community to simulate photogeneration.…”

“…and thus, accelerated ageing tests design is not straightforward. A conventional technique used by the CPV community for simulating cell photogeneration ageing deals with active storage, in which cells are current-biased during the accelerated tests [3]- [7]. However, such a bias is quite different from operating conditions [6].…”

“…However, such a bias is quite different from operating conditions [6]. Passive thermal storage has also been considered but was demonstrated to be more aggressive to CPV cells compared to active storage [7]. Therefore, no perfect solution exists and ageing tests need to be considered with hindsight.…”

Challenges in the design of concentrator photovoltaic (CPV) modules to achieve highest efficiencies

“…In the experiments at high humidity and temperature, oxidation of germanium and corrosion of the front side metallization occurred which is relevant for both structures. 210,211…”