Transmission Electron Microscopy of Amorphous Tandem Thin-Film Silicon Modules Produced by A Roll-to-Roll Process on Plastic Foil

An improvement of the photo-current is expected when amorphous silicon solar cells are grown on a ZnO texture. A full understanding of the relationship between cell structure and electrical performance is essential for the rapid development of high efficiency VHF-tandem cells on textured substrates. At first, we present the systematic study where amorphous cells are grown on ZnO based textures. For varying the texture, the same original master LPCVD ZnO was successively transferred to nickel molds and finally transferred to the plastic foil by roll-to-roll process. From TEM images, we show how a control-lost of shape fidelity is used to smooth the texture and make it compatible with subsequent layer growth. Then, we present the electrical performances of the most promising reference solar cell single junction which was obtained on a roll-to-roll foil. Finally, a tandem amorphous/amorphous Si reference cell was produced on textured foil with a stable efficiency of 8%. The first PV modules on UV textured plastic foil with aluminium back reflector were also produced with initial efficiency of 7%.