C. Scholten, L. Houben, M. Luysberg

The structural properties of high efficiency microcrystalline nip solar cells grown by plasma enhanced chemica1 vapor deposition are investigated by transmission electron microscopy, X-ray diffraction, and Raman spectroscopy. Surprisingly, solar cells with the highest efficiency of about 8% do not have the highest degree of crystallinity. Best performance is achieved at a crystalline volume fraction of about 70%, where sma11 crysta1line columns are surrounded by amorphous materia1. In general, the microstructure of all solar cells investigated is greatly affected by the nucleation onto the highly crystalline n-layers. Even under nearly amorphous deposition conditions of the i-layer individual crystalline columns extend throughout the whole solar cell.