Study on the Influence of the Luminescence Coupling in Dual Junction Solar Cells

The multijunction solar cell concept has proven to be a very efficient way of converting solar into electrical energy. Theoretical calculations using the detailed balance model aim in the optimization process of finding the best materials (in terms of bandgap energies) to compose the device junctions. However, along with other simplifications, such model applied to multijunction solar cells fails in considering one important physical effect: the luminescence coupling amongst the junctions. In this work, we present a method based on a self-consistent numerical approach for implementing the luminescence coupling in the detailed balance model applied to multijunction solar cells. We show results on the influence of the effect on the performance of different dual junction solar cells in which a coupling factor and the junction bandgap energies are varied. Therefore, we show that the main impact of the luminescence coupling is in the raise of the solar cell short circuit current, and consequently, their conversion efficiencies. Moreover, we highlight that the influence of the effect is more important for the bandgap energy combinations that would lead to low efficiencies. This is an important result towards the choice of materials by allowing more combinations to achieve high efficiencies.