Beyond Si, GE and GaAs single junction cells, multi junction (MJ) solar cells have gained rapid acceptance in the space power industry due to their 30% higher efficiency. To fully understand their behavior in radiation environment. The characterization and degradation of MJ devices are much more complex than single junction cells because of their sensitivity to light spectrum and different radiosensitivity of each junction.
Recently, the relationship between degradation is described by the change of short contacts. IC, VOC and radiation flux of Ge, Si, GaAs and GaInP batteries φ In this paper, we propose to use electroluminescence to measure the irradiation induced degradation of triple junction GaInP / GaAs / gephotovoltaic cells to detect the degradation of each single junction.
We give the research principle based on electroluminescence. Firstly, the electroluminescence intensity is related to the concentration of non radiative recombination centers in the cell node, which is the direct cause of gaas mj cell degradation. Secondly, electroluminescence technology can provide direct information of each individual junction constituting MJ battery independently of other junctions. In fact, the current voltage characteristics and spectral response of a given junction are not independent of the states of other junctions in MJ cell.
Electroluminescence are often a way that permits independent monitoring of degradation of every individual cell during a gaas mj cell and extraction of parameters characterizing such degradation. So, for GaInP / GaAs / Ge battery, we've proved that GE battery doesn't play a task within the degradation of MJ battery, and gainpcell begins to degrade about 3 × 1013 cm-2 for 1 MeV electron. The degradation of MJ battery is especially thanks to GaAs junction.
Therefore, these conclusions illustrate the way that MJ can have resistance: its global resistance is that the resistance of the battery whose current is that the limiting factor, and MJ battery should be constructed in such how that rock bottom current is provided by the junction of the fabric showing the utmost current to resist radiation. Obviously, other characteristics are needed to maximise the efficiency of multijunction devices. for instance , it's desirable to style each junction to supply an equivalent amount of photocurrent. This current matching depends on many factors, but the foremost notable ones are the band gap of the semiconductor, the absorptivity of the fabric and therefore the thickness of the gaas mj cell.