IEC 62787-2021 Concentrator photovoltaic (CPV) solar cells and cell on carrier (CoC) assemblies – Qualification (IEC 62787:2021).
5 Sampling
Device samples used in qualification testing shall be selected randomly in accordance with IEC 61 1 93-2 from a minimum of two manufacturing batches and subjected to the defined Process Identification Document (PID) manufacturing and screening steps.
The number of devices to be tested in each qualification test shall not be less than the sample sizes specified in Clause 8. In order to provide statistical meaning to the number of devices, IEC 61 1 93-2 has been used since it assigns a defect probability as a function of number of samples. The samples for each test of Table 1 and Table 2 shall be chosen randomly from the qualification lot. The qualification lot shall be a production lot of at least 1 000 bare cells/CoCs. The production lot shall be formed from at least two epitaxial runs and three metal/ARC depositions carried out in different weeks.
6 Marking Due to the very small bare solar cell dimensions any marking on cell is usually not possible. Therefore, an ID mapping needs to be applied. Regarding CoC under test, they shall be clearly marked or identified for later tracking of data records. The required information for both bare cells and CoCs are:
– name, monogram, or symbol of manufacturer;
– type or model number;
– serial number;
– polarity of terminals or leads;
– the date, place of manufacture, and cell materials should be marked, or be traceable from the serial number.
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 1 00 W/cm 2 = 1 000 suns. IEC 62787 pdf download.