Comparison of indoor and outdoor power measurements of thin film modules

Stabilised electrical performance data are necessary to compare different types of modules in the emerging thin-film PV market and as basic information for energy yield calculations. The problems with accurate power measurements of thin-film modules are well known. The module test-standard IEC 61646 ed. 2 tries to take these into account by demanding light-soaking and repeated STC-measurements which leads to time consuming procedures. The stabilisation behaviour over time of Isc, Voc, efficiency and filling-factor is compared under the influence of different illuminations. Therefore, IV-curves are measured with a high frequency during outdoor exposition and indoor exposition to 1000 W/m² irradiation from a class B solar simulator in a climatic cabinet under temperature-controlled conditions. The results are compared with STC-measurements after different pre-conditioning procedures. It turned out that the different module types behave differently with respect to the changes of their properties as a function of light-soaking exposure time.