THIN-FILM HYDROGENATED SILICON SULFUR ALLOYS AS PROMISING MATERIALS FOR SOLAR-CELL APPLICATIONS

Compositionally graded hydrogenated amorphous silicon-sulphur alloys were grown by r.f. glow discharge decomposition of silane and hydrogen sulphide at a substrate temperature of 250-degrees-C. The composition of the alloys was controlled by changing the gas volume ratio R(v) = [H2S]/[SiH4]. IR spectra reveal clear evidence for the incorporation of sulphur in the form of Si-S bonds in the material. Although there is a decrease in the photoconductivity sigma-ph with increasing E(opt), the photosensitivity sigma-ph/sigma-d remains high, exceeding 10(3) throughout the whole alloy range. The compositionally graded layers display high photosensitivities, indicating that they may be of use in amorphous-silicon-based solar cells.