The hot-wire cell method has been developed to grow polycrystalline and amorphous Si thin films with relatively high growth rates of 0.4-3.0 nm s(-1). It was found that polycrystalline Si films can be obtained at substrate temperatures of 175-400 degreesC without hydrogen dilution when the filament temperature is 2000-2100 degreesC. Valency control has been carried out using PH3 and B2H6. Up to now, high conductivities of 13 and 4 S cm(-1) have been achieved for n-and p-type polycrystalline Si thin films, respectively. Superstrate-type polycrystalline Si and amorphous Si solar cells prepared with deposition rates of 0.4-1.0 nm s(-1) showed efficiencies of 1.6 and 4.3% under AM1.5 illumination, respectively. We found by SIMS analysis that a high concentration of O and C atoms, of the order of 10(20)-10(21) cm(-3), is incorporated into the film, which limits the performance of the present cell.