Effect of hydrogen dilution in silane on light induced degradation of hydrogenated amorphous silicon films for solar photovoltaic applications

Abstract

Hydrogenated amorphous silicon films (a-Si:H) have been deposited by r.f. glow discharge of silane (SiH₄) and hydrogen (H₂) gas mixture. The hydrogen concentration in the gas mixture and the applied r.f. power density have been varied. The initial photoconductivity (σ_p), photosensitivity (σ_p/σ_d ), activation energy (E_a), optical band gap (E_g), hydrogen concentration, sub band gap absorption, Urbach energy (E₀) and defect density of the films have been measured, and the degradation, i.e., the reduction of photoconductivity under AM-I (100 mW/cm²) white light, has been studied. Films prepared with 95% hydrogen dilution and 6O mW/cm² r.f power density show the lowest degradation.