Quantitative loss analysis of voltage output characteristics on multi-junction solar cells

Owing to the improvement of device design and material properties, the conversion efficiencies of state-of-the-art solar cells are approaching the theoretical limit. However, identification of the remaining losses is still difficult. Therefore, the quantitative analysis of losses is important for further optimization of the conversion efficiencies. In this study, we propose a method to quantitatively analyze the losses in open-circuit voltage of multi-junction solar cells. This method employs absolute electroluminescence and external quantum efficiency measurements including uncertainties. We analyze the voltage output losses for three triple-junction solar cells and discuss possible improvements of multi-junction solar cells.