Accuracy evaluations for standardization of multi-junction solar-cell characterizations via absolute electroluminescence

Absolute electroluminescence (EL) measurements have been becoming essential methods to evaluate internal properties of individual subcells in multi-junction (MJ) solar cells. To establish methodology of absolute EL for standardization of MJ solar-cell characterizations, we developed independently calibrated absolute EL methods and verified accuracy and uncertainties via round-robin studies measuring EL emission rates for InGaP/GaAs/Ge triple-junction and single-junction solar cells. The results showed good quantitative agreements within 10% discrepancy among the individually calibrated methods, which corresponds to less-3-meV uncertainties in the estimation of the open-circuit voltages. This enables accurate comparison of the deviations between the open-circuit voltages via the transport experiment and via the absolute EL methods and detailed characterization of the internal properties of MJ solar cells.