This work presents the results of the first interlaboratory comparison of linearity measurements of short-circuit current versus irradiance that includes a wide variety of photovoltaic (PV) device types, from reference cells to full-size modules. The aim of this inter-comparison was to compare the methods employed and to collect new inputs useful for the revision of the standard IEC 60904-10, which deals with linearity measurements for PV devices. The procedures and facilities employed by the partners include the differential spectral responsivity, the white light response, the solar simulator method and the two-lamp method. The facilities are generically described and compared and their main sources of uncertainty are discussed. Comparison results show good agreement within declared uncertainties between all partners. A few minor exceptions under low-light conditions raise questions of possible uncertainty underestimation for these specific conditions. The overall outcome of the comparison also highlights the importance of considering correlations in the uncertainty budget, which can potentially improve the overall stated uncertainty. A critical review is made of the data analysis adopted in the standard IEC 60904-10 to calculate the linearity degree of the short-circuit current towards irradiance. The analysis review suggests a way to make results based on different methods more comparable and less prone to erroneous linearity assessment.

Today's variety of photovoltaic (PV) technologies imposes new challenges to laboratories and industries to precisely measure the performance of devices and, consequently, to accurately estimate the energy yield once installed in a specific location. Spectroradiometry has become a key discipline for metrology applied to PV: Spectral irradiance is one of the three parameters according to which solar simulators are classified according to IEC 60904‐9; precise spectrum measurements are a key factor in the spectral mismatch calculation. Finally, energy rating calculations according to IEC 61853 involve spectral irradiance conditions different than the AM1.5G standard spectrum. To tackle these issues, since 2011, the International Spectroradiometer Interlaboratory Comparison (ISRC) takes place annually in different locations of Europe with the participation of laboratories, research institutes, and industry partners to assess spectral measurement capabilities and share good measurement practices and protocols. In this paper, several results of the 9th ISRC 2019 are presented, looking in particular at the impact on characterization of new technologies like organic devices (OPV), dye‐sensitized (DSSC), and perovskites.

Although photovoltaic (PV) devices are rated at standard testing conditions (STCs), these STCs are rarely met, either outdoors, or when PV devices are used for indoor applications. Thus, it is beneficial to fully characterise the linearity of PV devices with respect to irradiance. Moreover, high accuracy linearity measurements are essential for reference cells (RCs), as they ensure the precision of the measured irradiance. This work presents a new technique for linearity measurements of PV devices based on digital light processing (DLP). The proposed system uses a digital micromirror device coupled with projection optics and a high-power LED array. By creating a series of patterns projected on the device under test with a specific number of bright and dark pixels, linearity measurements can be implemented through a spatial dithering process. Since the dithering process is mechanical, it is expected that any spectral variability effects for the different dithering levels or electrical non-linearities of the light source are avoided. The developed system can provide thousands of measurement points on the linearity curve of a device in seconds, which is impossible with any other currently established methods. Measurements of RCs with known linearity curves are acquired and are validated by conventional methods. Results demonstrate that the DLP method provides equal measurement accuracy compared to conventional systems, but at significantly higher resolution (points on the linearity curve) and order of magnitude higher measurement speed.

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