This part of IEC 60904 gives guidance for the measurement of the spectral responsivity (SR) of multi-junction photovoltaic devices. It is principally intended for non-concentrating devices, but parts may be applicable also to concentrating multi-junction PV devices. The SR is required for analysis of measured current-voltage characteristics of multi-junction PV devices as described in IEC 60904-1-1. The requirements for measurement of SR of single-junction PV devices are covered by IEC 60904-8, whereas this document describes the additional requirements for the measurement of SR of multi-junction PV devices. This document only considers the measurement of SR of individual junction layers within a two-terminal multi-junction device. This document may be applicable to PV devices designed for use under concentrated irradiation if they are measured without the optics for concentration.