Rigorous optimization of InGaN multijunction solar cells efficiency
Résumé
The InGaN ternary alloy has the potentiality to achieve high efficiency solar cells. Indeed the bandgap of the InGaN alloy covers the whole solar spectrum including the visible region by changing the Indium composition. The InGaN alloy also counts among its advantages a relatively low effective mass of electrons and holes, their high mobilities, high absorption coefficients as well as radiation tolerance. These very promising characteristics give the possibility to design and develop next-generation high-efficiency thin films solar cells, based on multijunction technology. However, the main drawback is the difficulty of p-doping and the high defects density in these III-Nitride alloys. In this report, we develop a novel and rigorous optimization approach based on state-of-the-art optimization algorithms, to design an optimal multijunction solar cell based on InGaN alloys. This approach allows to automatically determine the values of the cell parameters, among which are the geometries of the active layers, their doping and defect levels, to maximize its efficiency within the possibilities of actual device fabrication. We have found that the use of this rigorous optimization approach is necessary because of the high dependence of the cell efficiency on the device geometry, doping and defects, particularly concerning the top and bottom P layers properties