NOVELTY - New silane compositions comprising specified silane compounds, and silane compound(s) selected from cyclopentasilane, cyclohexasilane and silylcyclopentasilane.    USE - For semiconductor thin films used in solar cells (claimed). The composition may also be used in electronic devices such as large scale integrated circuits, thin film transistors and photodetectors,    ADVANTAGE - The silicon film forming method does not require an energy-consuming expensive and bulky device, can be applied to the production of a substrate having a large area and is capable of forming a silicon film with ease.    DETAILED DESCRIPTION - A silane composition comprises:    (A) a compound selected from:    (I) a polysilane compound of formula (I); or    (II) a product formed by the exposure (photo-irradiation) of a silane compound selected from:    (a) a hydrogenated chain silane compound of formula (IIa);    (b) a hydrogenated cyclic silane compound of formula (IIb);    (c) Si4H4; or    (d) a hydrogenated cage-like silane compound of formula (IId); and    (B) silane compound(s) selected from cyclopentasilane, cyclohexasilane and silylcyclopentasilane.    SinRm (I)    SiiH2i+2 (IIa)    SijH2j (IIb)    SikHk (IId)    n = at least 3;    m = n-(2n+2);    R = H, alkyl, phenyl, or halo;    i = 2-8;    j = 3-10;    k = 6, 8, or 10;    In formula (I), when all R's are hydrogen atoms, and m = 2n, then n at least 7.    INDEPENDENT CLAIMS are also included for:    (1) the formation of a silicon film on a substrate, comprises coating the silane composition on a substrate and treating it with heat and/or light in a non-oxidizing atmosphere;    (2) the formation of a silicon oxide film on a substrate, comprises coating the silane composition on a substrate and treating it with heat and/or light in an atmosphere containing oxygen and/or ozone; and    (3) the production of a solar cell comprising semiconductor thin films having different concentrations and/or types of impurity, laminated between a pair of electrodes. At least one of the semiconductor thin films are formed by coating the silane composition on a substrate and treating the coating film with heat and/or light.