FINE-TUNING OF MULTI-JUNCTION SOLAR CELLS: A THEORETICAL ASSESSMENT

The typical number of subcells comprised in multijunction solar cells steadily increased over the last 25 years to achieve higher electrical efficiencies. However, these cells typically show increased sensitivity to the spectral content of sunlight, and the efficiency under real conditions can be significantly affected. This study investigates whether or not fine-tuning of MJ solar cells could lead to significant improvement in the energy yield of CPV systems comprising a high number of subcells. The average incident spectrum in several cities is obtained with SMARTS, using as an input the main atmospheric parameters from AERONET database. The optimal combinations of bandgaps for all the selected locations and cell architectures comprising up to 10 subcells was derived. In particular, the improvement in the energy output achieved when using fine-tuned MJ solar cells to a mean annual spectrum in a located area is investigated. Implications for future generations for multi-junction solar cells are also discussed.