External Quantum Efficiency and First Results of Electric Performance Measurements on a Quadruple Junction Space Solar Cell

External Quantum Efficiency (EQE) and Current-Voltage (I-V) measurements of a monolithic quadruple junction (4J) space solar cell AlGaInP (J1)/ AlInGaAs (J2) / InGaAs (J3) / Ge (J4) manufactured by CESI (Milano, Italy) have been performed at INTA-Spasolab. In order to determine electrical cell performance of this 4J solar cell type under AM0 irradiance and cell temperature standard conditions, the external quantum efficiency (EQE) measurement system and steady-state solar simulators at the cell testing laboratory INTA-Spasolab are to be upgraded. The purpose of this work is to present both the upgrading of INTA-Spasolab facilities and the results of the characterization of a 4J solar cell under development.