(JP10294484-A)      The cell includes a p-type semiconductor layer (104), an i-type semiconductor layer (103) and an n type semiconductor layer (107) which are laminated sequentially. The i-type semiconductor layer consists of non-mono crystal semiconductor. The mean diameter and distribution of crystal grain in the i-type semiconductor layer is uneven.    ADVANTAGE -   Improves operation speed of photovoltaic cell. Offers inexpensive photovoltaic cell with superior photoelectric conversion efficiency. Improves light stability. Excels in mass production.    (US6043427-A)      The photovoltaic device has a pin-structure semiconductor layer formed by superposing a p-type semiconductor layer, an i-type semiconductor layer and an n-type semiconductor layer. The i-type semiconductor layer comprises a non-single crystal semiconductor e.g. silicon and average grain size distribution of crystal grains of the i-type semiconductor layer is not uniform in the film thickness direction. The average grain size of the crystal grains in the i-type semiconductor layer in a region near the interface of the i-type semiconductor layer and the p-type semiconductor layer and/or that of the i-type semiconductor layer and the n-type semiconductor layer is greater than the average grain size of the crystal grains in the which remains regions of the i-type semiconductor layer. The hydrogen content of the region with the largest average grain size in the i-type semiconductor layer is 10 % or less and the hydrogen content of the which remains regions of the i-type semiconductor is between 3 and 20 %.    The ratio of the smallest average grain size to the largest average grain size is 0.9 or less. The non-single crystal semiconductor comprises microcrystalline semiconductor with the largest average grain size between 20 angstroms and 1 m, and microcrystalline semiconductor or polycrystalline semiconductor with the largest average grain size between 50 angstroms and 10 mm. The dopant concentration in a region in the i-type semiconductor layer located near the interface of the n-type semiconductor is 2 x1017 cm-3 or less. The i-type semiconductor layer is formed by high frequency plasma CVD under the conditions of a frequency between 50 and 2,450 MHz, pressure between 0.001 and 0.5 Torr and a making power density between 0.001 and 0.5 W/cm3.    ADVANTAGE -   Increases photostability. Increases speed of production while maintaining characteristics of device and materials. Increases short circuit current, open circuit voltage and conversion efficiency.