Degradation analysis of GaAs solar cells at thermal stress

The work focuses on the study of structure stability and electrical parameters of photovoltaic cells based on GaAs with Ge substrate. Solar cells of this type are used especially in adverse environments such as space applications, so their working parameters should be stable even under extreme operating conditions. Changes of electrical characteristics of the cells were recorded in the form of noise measurements for examination of distinctions in the pn-junction. Current-voltage characteristics under the light illumination and in the dark environment for comparison of the cells performance were also measured. Infrared camera showed the thermal irradiation of the stressed and damaged parts and support to localize the defected areas. Atomic force microscope (AFM) was applied for observation of changes in three-dimensional topography with high resolution. Scanning electron microscope (SEM) with energy-dispersive X-ray spectroscopy (EDS) showed morphology of the solar cells and provided the elemental analysis of the samples. Raman spectroscopy provided a structural fingerprint and helped to evaluate the influence of induced degradation methods. Variations of morphology and composition were compared, detected and well-observed. Furthermore, electrical measurements proved the solar cells to be stable under temperature stresses.