Transition films from amporphous to microcrystalline silicon and solar cells

A series of hydrogenated silicon films near the threshold of crystallinity was p repared by very high frequency plasma-enhanced chemical vapor deposition (VHF-PE CVD)from a mixture of SiH4 diluted in H2. The effect of h ydrogen di lution ratios R= ［H2］/［SiH4］ on the microstructure o f the films was investigated. The photoelectronic properties and stability of the film s were studied as a function of crystalline fraction. The results show that t he diphasic films gain both the fine photoelectric properties like a-Si:H an d high stability like μc-Si:H. By using the diphasic silicon films as the intrinsic layer, p-i-n junction solar cells were prepared. Current-voltage (J-V) characteristics and stability of the solar cells were measured under an AM15 solar simulator. We observed a light-induced increase of 52% in the ope n-circuit voltage (Voc) and a light-induced degradation of ～29% in efficiency.