Spectral responsivity measurements of monolithic GaInP_2/InGaAs/Ge triple-junction solar cells

摘要

GaInP_2/InGaAs/Ge triple-junction solar cells have become the main energy source for space on-orbit applications. Forthe sake of the three composed sub-cells, including GaInP_2, InGaAs and Ge sub-cell, the monolithic triple-junction solarcells can make use of solar irradiance in the wavelength range of 300 nm to 1800 nm. Before assembled into space solararrays, each solar cell’s current-voltage curves should be measured in laboratories on earth by AM0 solar simulators, toknow their key parameters especially short circuit current. Solar cell’s current-matching is crucial for assembling intoarrays. While spectral responsivity is essential for spectral mismatch factors (MMFs) calculation during the currentvoltagemeasurement. MMF corresponding to each sub-cell should be analyzed, so spectral responsivity of each sub-cellof monolithic solar cell was required to be measured out. But sub-cells are connected in series in a monolithic multijunctionsolar cell, and current-limiting effect makes traditional spectral responsivity measurement which is suitable forsingle-junction solar cells not applicable anymore. For measuring the spectral responsivity of monolithic multi-junctionsolar cells, optimized bias light and bias voltage are required to make the tested target sub-cell be the current-limitingone. The wavelength range and irradiance intensity of the bias light, the direction and value of the bias voltage, should bechose and adjusted appropriately during the measurement, otherwise will lead to measurement artifacts and obtainincorrect results. In this paper, combing optimization of bias light and bias voltage with monochromatic light system, wewould present method and detailed procedures for measuring the spectral responsivity of monolithic GaInP_2/InGaAs/Getriple-junction space solar cells.