IEC 62787:2021 pdf download

IEC 62787:2021 pdf download.Concentrator photovoltaic (CPV) solar cells and cell on carrier (CoC) assemblies – qualification
1 Scope
This document specifies the minimum requirements for the qualification of concentrator photovoltaic (CPV) cells and Cell on Carrier (CoC) assemblies for incorporation into CPV receivers, modules and systems. The object of this qualification standard is to determine the optoelectronic, mechanical, thermal, and processing characteristics of CPV cells and CoCs to show that they are capable of withstanding assembly processes and CPV application environments. The qualification tests of this document are designed to demonstrate that cells or CoCs are suitable for typical assembly processes, and when properly assembled, are capable of passing IEC 62108. This document defines qualification testing for two levels of concentrator photovoltaic device assembly: a) cell, or bare cell; and b) cell on carrier (CoC). NOTE etc.
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. Illumination I-V curve has to be performed before and after qualification tests. The focus of the illumination I-V curve is on the relative power degradation, not on the absolute power output. The relative power degradation, P d , is defined as follows: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. 7.3.2 Procedure If the dark I-V is used for diagnostic purpose, it should be measured during initial measurements to establish a reference for later dark I-Vs. a) Choose a suitable power source, which could be a conventional DC power supply, as long as it will generate current up to 1,5 times the rated current point corresponding to the photocurrent at the specified maximum concentration. The current should be adjustable so that there are at least 30 separate points in the range of 10 -4 to 1,5 times rated I sc at the specified maximum concentration. The interval of the points should be nearly equal-spaced with a lower pitch around I sc ; b) For CoCs, short the blocking diode by placing a jumper lead across the leads of the blocking diode, if there is one installed;