This part of IEC 60904 applies to the following photovoltaic devices for terrestrial applications:– solar cells with or without a protective cover;– sub-assemblies of solar cells;– modules;– systems.NOTE The term “test specimen” is used to denote any of these devices.The principles contained in this standard cover testing in both natural and simulated sunlight.This standard is not applicable to solar cells designed for operation in concentrated sunlight or to modules embodying concentrators.Photovoltaic conversion is spectrally selective due to the nature of the semiconductor materials used in PV solar cells and modules. To compare the relative performance