The electrical output of photovoltaic devices is dependent on the spectral content of the source illumination and its intensity. To make accurate measurements of the performance of photovoltaic devices under a variety of light sources, it is necessary to account for the error in the short-circuit current that occurs if the relative spectral response of the primary reference cell is not identical to the spectral response of the cell to be calibrated. A similar error occurs if the spectral irradiance distribution of the test light source is not identical to the desired reference spectral irradiance distribution. These errors are accounted for by the spectral mismatch parameter M (Test Method E 973), a quantitative measure of the error in the short-circuit current measurement. It is the intent of this test method to provide a recognized procedure for calibrating, characterizing, and reporting the calibration data for secondary photovoltaic reference cells.

A secondary reference cell is calibrated to the same reference spectral irradiance distribution as the primary reference cell used during the calibration. Primary reference cells can be calibrated by use of Test Method E 1125 or Test Method E 1039.

Note 1—No standards for calibration of reference cells to the extraterrestrial spectral irradiance distribution presently exist.

A secondary reference cell should be recalibrated yearly, or every six months if the cell is in continuous use outdoors.

Recommended physical characteristics of reference cells are provided in Specification E 1040.

Because silicon solar cells made on p-type substrates are susceptible to a loss of I_sc upon initial exposure to light, it is required that newly manufactured reference cells be light soaked at an irradiance level greater than 850 W/m² for 2 h prior to initial charcterization in Section 7.

1.1 This test method covers calibration and characterization of secondary terrestrial photovoltaic reference cells to a desired reference spectral irradiance distribution. The recommended physical requirements for these reference cells are described in Specification E 1040. Reference cells are principally used in the determination of the electrical performance of a photovoltaic device.

1.2 Secondary reference cells are calibrated indoors using simulated sunlight or outdoors in natural sunlight by reference to a primary reference cell previously calibrated to the same desired reference spectral irradiance distribution.

1.3 Secondary reference cells calibrated according to this test method will have the same radiometric traceability as the of the primary reference cell used for the calibration. Therefore, if the primary reference cell is traceable to the World Radiometric Reference (WRR, see Test Method E 816), the resulting secondary reference cell will also be traceable to the WRR.

1.4 This test method applies only to the calibration of a photovoltaic cell that demonstrates a linear short-circuit current versus irradiance characteristic over its intended range of use, as defined in Test Method E 1143.

1.5 This test method applies only to the calibration of a photovoltaic cell that has been fabricated using a single photovoltaic junction.

1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.