Methods of linear dependence and linearity measurements
IEC 60904-10-2020 pdf download.Photovoftaic devices — Part 10: Methods of linear dependence and linearity measurements
Disposltif photovoltaIques — Partie 10: Méthodes de mesure de Ia dépendance Iinéaire et de Ia linéarité.
5.1 General requirements common to all procedures
The following requirements and recommendations are valid for all linear dependences and for all measurement procedures, unless explicitly specified differently. Requirements and recommendations that are specific to the apparatuses used for each type of measurement are given in the following subclauses.
Light sources characterised by Intense peaks over a broad continuum, like for example Xenon sources or some lamps based on light emitting diodes (LEDs), should be carefully evaluated before use. Indeed, for some PV devices and/or technologies the spectral responsivity can vary with temperature as well as with irradiance level. Therefore, it can pass through various emission lines in the lamp spectrum as temperature or irradiance varies. When this occurs, it can cause shifts in performance that are related mainly to a change in the interaction between the band gap region of the spectral responsivity and the actual spectral irradiance in the same wavelength range. If this possibility is not properly assessed in each specific case, such shifts could be misinterpreted as deviations from the linear dependence while they are not. However, based on the measured DUT spectral responsivity as a function of temperature or of irradiance (depending on what applies) and on the measured spectral irradiance, the magnitude of this effect can be calculated by performing a SMM calculation according to IEC 60904-7 as a function of temperature or of irradiance (depending on what applies). Some guidance on how to do this is reported in the Bibliography. The SMM calculation can then be applied as SMM correction to every single measurement at all temperatures different from 25 °C or irradiance levels other than 1 000 W/m2 (depending on what applies). If the change in SMM is not larger than 1 % over the entire range of temperatures or than ±0,5 % for irradiances, it may alternatively be included as component of the SMM uncertainty in the measurement uncertainty calculation.
EXAMPLE Crystalline silicon’s band gap is known to shift due to temperature changes.
When the test parameter is the irradiance, the equipment and procedure used to change irradiance are to be verified with a spectroradiometer. This applies to all measurement procedures other than the two-lamp and N-lamp methods both applied to single cells and other than the linearity measurement by means of differential spectral responsivity. A radiometer is allowed as alternative to the spectroradiometer only if the following conditions are both met:
a) the reference device is spectrally-matched to the DUT, and
b) the setup to measure the linearity is a solar simulator used only with filtering elements neutral with respect to the spectrum of the light.
To reduce the change in the heat load in all measurements where the irradiance is the test parameter, and therefore to improve the temperature stabilization of the DUT over the whole measurement sequence, it can be useful to reduce the infrared portion of the light whose energy is below the OUT’s energy band gap by interposing suitable filters between the light beam and the test plane.IEC 60904-10-2020 pdf download.