IEC 60904-1-2020 Photovoltaic devices – Part 1: Measurement of photovoltaic current-voltage characteristics.
a) When the measurements are intended to be reported at standard test conditions (see 4.5) the in-plane average irradiance during measurement shall be between 800 W∙m −2 and 1 200 W∙m −2 to minimise errors arising from large corrections.
b) Temperature sensors should be located so as to detect as closely as possible the temperature of the respective device cell junction. If a temperature gradient between the sensor and the cell junction is suspected, an appropriate contribution to the measurement uncertainty should be included. Consideration should also be given to any possible non- uniformity of temperature across either device, particularly for PV modules, where the temperature of individual cells can vary due to their electrical characteristics, particularly when the module is illuminated under short-circuit conditions. The Equivalent Cell Temperature (ECT) method specified in IEC 60904-5 can be useful in dealing with either a temperature gradient or temperature non-uniformity. The cooling effect from airflow (for example due to wind during outdoor measurement or due to air conditioning of the room for indoor measurements) on the temperature sensors should be considered in the uncertainty of the temperature measurement.
c) The active surface of the device under test shall be coplanar within ±2° with the active surface of the reference device. d) Voltages and currents shall be measured using independent leads from the terminals of the device under test and keeping them as short as possible. If the device under test is a module, a subassembly or an encapsulated solar cell, the 4-wire connection should start at the terminals or connectors. If the device under test is a bare PV cell, the 4-wire connection should start at the cell bus bars. The connection method for bare cells (i.e. provided without connectors) should be carefully evaluated. Differences can occur if soldered tabs are used compared with non-soldered methods such as bars having contact springs or conductive plates having a large-area contact with the cell back contact. Non-soldered methods can result in higher fill factors than are observed in the module. The contacting method should be appropriate to the intended use of the cell or of the measurement. The contact method used (bare cells) or the contact point (modules) for 4-wire connection shall be stated in the report. For bare solar cells without busbars or cells with low surface conductivity such as multi-busbar cells, 4-wire connection should start at the contacting structure in order to avoid artificially increased fill factors in the measurement caused by voltage drop at the resistance between current and voltage probe on the cell. Possible deviations between the calibration of the measurement system (typically under static load conditions) and its use during I-V curve measurements (dynamic load conditions) shall be considered.IEC 60904-1 pdf download.