Simultaneous measurement of an internal quantum efficiency and an external quantum efficiency of a solar cell using an emitter that emits light; a three-way beam splitter that splits the light into solar cell light and reference light, wherein the solar cell light strikes the solar cell; a reference detector that detects the reference light; a reflectance detector that detects reflectance light, wherein the reflectance light comprises a portion of the solar cell light reflected off the solar cell; a source meter operatively coupled to the solar cell; a multiplexer operatively coupled to the solar cell, the reference detector, and the reflectance detector; and a computing device that simultaneously computes the internal quantum efficiency and the external quantum efficiency of the solar cell.