Reverse and Forward Modelling of Multijunction Solar Cells with Ecosim

Abstract

This paper presents a model of a triple junction solar cell including the reverse performance. Several situations derive from the series association of subcells within a multijunction solar cell, among others, that the cell limiting in current might be reverse biased under certain operational conditions. The subcell limiting can change due to varying spectral measurement conditions or because of different degradation rates of the subcells at end of life. The model described here is based on Ecosim and allows a complete simulation of the current-voltage characteristic of the solar cell, taking into account the reverse performance. This model offers a tool to assess the impact of different spectral conditions on the current-voltage characteristic of the solar cell that might occur in long duration tests under illumination. The modelling validation has been supported with measurements of triple junction solar cells and components performed in ESTEC laboratories. In summary, the core idea of the paper is to extend the modelling of the solar cell to reverse voltages, obtaining thus a tool that can reproduce the performance of the cell in all possible bias conditions.