The instantaneous performance ratio of thin-film photovoltaic modules of three different technologies is analyzed and characterized using contour graphs for different outdoor conditions. This parameter changes when modules are working in outdoor conditions depending on several variables. The most explanatory parameters we have found are the module temperature, the atmospheric clearness index and the solar spectral irradiance distribution; this latter has been included in the characterization using the average photon energy index as it has been identified as a good indicator of the solar spectral irradiance distribution. Moreover, the variance of instantaneous performance ratio for each studied technology has been analyzed. We can conclude that the joint use of all these parameters in contour graphs allows us to better characterize the performance of modules and to reduce the uncertainty observed in previous proposals that only use two of these parameters.
