A test apparatus for analyzing performance of a multi-junction solar cell can include a plurality of light source groups, each light source group including three or more light sources distributed over a substrate. Each sub-cell of the solar cell is associated with at least one of the light source groups, and each light source group primarily photoexcites the sub-cell of the light source group with which it is associated. The intensities of the various light source groups can are adjusted such that an output current of each of a plurality of calibration standards is within 2% of a predetermined current value. The test apparatus can then be used to test performance of the multi-junction solar cell.