This part of IEC 60904 describes procedures for measuring the light-induced degradation (LID) of crystalline silicon photovoltaic (PV) cells in simulated sunlight. The magnitude of LID in a crystalline silicon PV cell is determined by comparing maximum output power at STC before, and after, exposure to simulated sunlight at a specified temperature and irradiance. The purpose of this standard is to provide standardized PV cell LID information to help PV module manufacturers in minimizing the mismatch between cells within the same module, thereby maximizing power yield. When compared to PV module LID measurement described in the IEC 61215 series, several extra experimental factors have been found to show significant impact on the PV cell LID test, which were not considered by IEC 61215-2. This standard provides a conditioning and measurement procedure and parameter settings required for consistent PV cell LID measurements. LID magnitude is one important factor of cell quality. However, it is not recommend using it as the sole determination factor. For example, compared to LID magnitude, quasi stabilized Imp and Pmp, along with their distributions, affect more directly to module quality.