The value of the optical transmittance in the range of the visible light 380-780 nm has been performed on different types of modules.

Due to the inhomogeneous nature and the presence of different materials, e. g. glass, EVA, the cell itself, it has been not very simple to get the value of transmittance. We prepared a methodology of measurements that has proved to be useful within the error given by the lighting project, that is less than 5 %. Details of the methodology can be found on a paper presented at the PVSEC conference in Paris 2004 in June.

Different kind of modules were considered and the figures shows the corresponding measured transparencies, depending on the bulk transparency of the materials used for the sandwich glass/EVA/glass, the density of the cells, that means the spacing, and the kind of module ( a double glazing module was also considered). The transmittance values for the transparent part of the modules is just a bit lower 90 %, a part the double glazed modules where it falls at 73 % due to a not very transparent encapsulant layers, fortunately not effective on the cells. Depending on the density of the cells, the ratio of the active area divided the module area, the transmittance of the components can change consequently.

The table 1 below shows some values of the optical transmittance