PV Performance Lab
Starting with the exciting question of the performance of solar cells and solar modules, in this working group we deal with further topics such as the longevity and reliability of solar modules of various technologies through to yield analyses of PV modules in different climate zones.
To characterize the performance of solar cells and solar modules, we use constant light and flash light solar simulators depending on the size and nature of the samples. All sun simulators achieve class A according to DIN EN 60904-9. We have extensive expertise in measuring the spectral responsivity of solar cells, especially stacked cells. We can measure the spectral responsivity on different measuring systems from cell size (typically 1 cm²) to mini module size (10 x 10 cm²).
We also have numerous luminescence and infrared-based imaging measurement methods (e.g. to determine the lifetime of minority charge carriers or to analyze losses).
A good understanding of physics is of utmost importance for the interpretation of measurements. We have extensive experience in the field of device simulation, from classical drift-diffusion in (disordered) semiconductors to industrial scale models for solar modules. We use a range of opto-electronic device simulators to model small cells. For large-scale device simulations, we use our in-house developed open-source simulation tool "Photovoltaic Module Simulator (PVMOS)".
In our virtual Reliability Laboratory, we have bundled our activities relating to reliability, defects and the development of defects in PV modules. These activities include long-term tests under continuous light to determine light-induced ageing (LID) and accelerated ageing experiments on solar cells in a climate chamber under the influence of temperature, light and humidity. At our PV module outdoor measuring station, we measure high-resolution current-voltage characteristics, module and ambient temperature as well as irradiance and spectrum. During reliability tests, we often observe the development and worsening of local defects, which are analyzed using state-of-the-art luminescence and infrared imaging techniques. In addition, we are developing new imaging luminescence and infrared measurement methods to quickly and quantitatively determine power losses and defects in PV modules. Some methods are particularly suitable for measurements in the field (e.g. quantitative daylight luminescence methods). These activities rely heavily on our expertise in power analysis and device simulation.
In addition to determining the performance of solar cells and reliability issues, we are also involved in the development of yield models and predictions. These yield models can be used to analyze field performance data or to predict energy yield. The long-term performance of solar cells is highly dependent on climatic conditions. For this reason, we use large datasets with performance data on a variety of solar technologies under different climatic conditions (see project PVKLlima). We develop efficient filtering methods for such datasets (e.g. to filter out measurement errors). The filtered datasets are analyzed to characterize the performance including (metastable) degradation effects and to verify the developed yield models.
