An investigation on structure and materials of laminated organic solar cell packaging

Polymer-based organic solar cells are attractive in that they can be manufactured on plastic substrates by a variety of printing techniques and thus inexpensive large-volume manufacturing should be possible. In order to reach cost-effective, flexible and stable organic photovoltaic device, mechanical properties of package structure and materials should be concerned. The flexibility of the structure and material properties like ultimate tensile strength, are closely connected to long-time reliability of photovoltaic device subjected to mechanical load. For these considerations, we are motivated to quantitatively analyze the mechanical behavior of structure and materials of a solar cell panel. In our research, a five-layered solar cell structure is studied. The functional part, which consists of a photo-active layer and two electrode layers, is protected by cover and substrate layers. Individual layers and the overall structure have been subjected to tensile loads, and tensile curves are recorded during the tests. Test results indicate that polymer-based layers, which include cover, photo-active and substrate layers, play a dominant role on feature of flexibility of organic solar cell. Indium tin oxide (ITO)-based electrode layers, which have elongation of only 0.2%, are the weakest parts of the overall package. Further studies by scanning electron microscope (SEM) reveal that the fracture surface of electrode layers is flat and smooth. This typical brittle feature in the fractograph is consistent with the macro behavior of the electrode layer. As electrode layers turn out to be the short slab of the package; transparent, conductive and flexible material such as carbon nanotube, graphene or nano silver wire can become possible candidates for electrodes of future organic solar cell, which can result in more reliable packaging modules and systems.