PD IEC TS 63202-4:2022

Photovoltaic cells. Measurement of light and elevated temperature induced degradation of crystalline silicon photovoltaic cells | Status: Current

1 Scope This part of IEC 63202 describes procedures for measuring the light and elevated temperature induced degradation (LETID) of crystalline silicon photovoltaic (PV) cells in simulated sunlight. The requirements for measuring initial light induced degradation (LID) of crystalline silicon PV cells are covered by IEC 63202‑1, where LID degradation risk of PV cells under moderate temperature and initial durations within termination criteria of 20 kWh·m−2 are evaluated. Energy yield of PV modules is significantly affected by the inherent LETID performance of the PV cells, which are used in it. This LETID performance includes LID and other degradation mechanisms. The procedures described in this document are to evaluate the degradation behaviour of PV cells under elevated temperature and longer duration of light irradiation. The degradation rate, maximum degradation ratio and possible regeneration are determined by comparing the cell maximum power, Pmax, at Standard Test Conditions (STC) during the light irradiation process with respect to the initial Pmax. A Pmax degradation profile with respect to cumulative irradiation is presented, which helps cell manufacturer to judge whether the cells are prone to LETID before being assembled into modules. Different from some other standards which separate boron-oxygen induced LID from LETID or are limited to charge carrier injection induced degradation [1]1, the overall degradation under light irradiation at elevated temperature is included in the procedures described in this document. The overall degradation, determined using this procedure, is more relevant to various degradation mechanisms under field condition and gives a better evaluation of LETID risk. For cells with strong initial degradation within around 20 kWh·m−2, the procedures to measure initial light induced degradation (LID) in IEC 63202‑1 can be applied. Compared with module LETID detection method described in IEC TS 63342, higher injection level under open-circuit condition is used to shorten the test duration, while the temperature is identical. The procedures described in this document can be used to detect the LETID risks of PV cells [2],[3] and to judge the effectiveness of LETID mitigation measures, e.g. quick test for production monitoring, thus helping improve the energy yield of PV modules.