A method to analyze current mismatch in a multijunction laser power converter based on I-V measurements

Multiple steps are observed in the I-V curves of current-mismatched six-junction InGaAs laser power converters with the voltage ranging from reverse breakdown voltage to open circuit voltage. The formation mechanism of the I-V curves is analyzed using a series-connected device model. The voltage drops across subcells can be significantly different at a certain current, and the steps represent the subcell photocurrents. The photocurrents of subcells are experimentally determined, and the degree of current mismatch is obtained for a multijunction laser power converter (MJLPC), which provides useful information for the design and fabrication of high-efficiency MJLPC. In addition, the absorption coefficient of InGaAs is extracted based on the current mismatch degrees at different temperatures, providing another way to determine the active layer absorption coefficient of an MJLPC.