IEC 62787-2021 pdf Concentrator photovoltaic (CPV) solar cells and cell on carrier (CoC) assemblies – qualification

7 Characterization methods for measuring the performance of bare cells and CoCs subjected to qualification tests 7.1 General The optoelectronic performance characterization based on illumination I-V curves tries to identify optoelectronic performance degradation of test samples caused by the required qualification tests. Therefore, illumination I-V curve has to be performed before and after qualification tests. The goal of the illumination I-V curve is on the relative power degradation, not on the absolute power output. Scanning Acoustic Microscopy (SAM) is also required but only for CoCs. In addition, electroluminescence mapping and dark I-V curve can provide diagnostic information about defects and changes within the device. Before and after qualification testing, dark I-V curve can be carried out for the voltage and current ranges of interest. Electroluminescence images are not explicitly suggested through this document, but they could be of great help when captured for each device at different current injection levels before and after some qualification tests. 7.2 Light I-V measurement This is a compulsory characterization method. All test samples shall be measured at 25 °C, under AM1.5D spectrum as specified in IEC 62670-1, and at an overall light intensity representative of the intended application. For the purposes of this characterization method, 1 sun equivalent of the AM1.5D spectrum will have a total power density (irradiance) of 0,1 W/cm 2 , so that a light intensity of 100 W/cm 2 = 1 000 suns. The parameters and measurement methods for the light I-V measurement are defined in IEC 60904-1-1:2017.
7.3 Dark I-V measurement General 7.3.1 This is a compulsory characterization method for the Electrostatic Discharge (ESD) Damage Threshold test while is optional for the rest. The high operating current density of CPV devices, can sometimes mask detection of low level defects or the onset of degradation. Dark I-V measurements performed before and after a qualification test can provide a more sensitive measure of damage or degradation. The dark I-V measurement is a cost-effective method to monitor and diagnose power degradation of bare solar cells and CoCs following intermediate stress tests, or to monitor the electric performance stability of the control samples.