The uncertainty of pyranometer measurements should be traced back to the World Radiation Reference (WRR), a standard that is specified by the mean sensitivity of the World Standard Group (WSG). The WSG is build up by 7 primary standard pyrheliometers, operated at Davos, Switzerland. Analyzing the complete calibration chain for an individual field pyranometer, usually the uncertainty of its calibration constant is extracted as a unique figure depending on the calibration method. The common representation of the expanded uncertainty, specified by the manufacturer is global information on the accuracy of daily averages. For the use of pyranometers for e.g. test of solar energy components as solar collectors, this information on the global daily accuracy of the pyranometer is not sufficient. As the response of a solar collector to the irradiance shows nonlinearities, a more detailed analysis of the pyranometer uncertainties is necessary. This will be demonstrated for the analysis of the uncertainties of the test results — i.e. the collector coefficients and their uncertainties — and the resulting predictions of the energy gain by these devices. Ancillary information by the manufacturers will be used to discuss the uncertainty of individual measurements depending on e.g. ranges of those parameters that originate the uncertainties, depending on the geometry (incidence angle), ambient temperature and the sky conditions. Based on this information the inter-comparability of test performed at different times or with different instruments will be discussed.

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In order to obtain significant improvements in the Power Conversion Efficiency (PCE) of solar cells, researchers should know in the future which material properties and cell design constitute cells with the highest possible efficiency. Such knowledge can be obtained by simulation and numerical optimization of the cells PCE, which is shown for a Perovskite Solar Cell (PSC) in a multidimensional variable space. By use of a sensitivity analysis, based on the analytical model of a PSC, it is shown that its efficiency is a nonlinear function of several variables in a multidimensional hypercube space. The numerical optimization presented increases the PCE from initially 15.7 % to 27.6 % in a nine-dimensional function space of material properties and absorber layer thickness. Here the combined variable specification necessary to obtain such a high efficiency is presented, and it is discussed how the manufacturing can be improved in order to successfully increase the cells PCE.Early research in hybrid solar cells 1-3 led to the concept of the perovskite-based solar cell 4 , and more recent advances in searching for new organic-inorganic hybrid semiconductor materials and properties for this type of cell 5-19 provided the steepest increase of power conversion efficiency (PCE) values in comparison to other solar cell types, reaching the state-of-the-art PCE of 22.1% 20 .

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