Stability of a-Si:H prepared by hot-wire and glow discharge using H₂ dilution evaluated by pulsed laser degradation

The quality of intrinsic amorphous silicon films prepared by different deposition techniques was investigated. For very high frequency glow discharge, both the substrate temperature as well as the hydrogen dilution were varied. These layers were compared to hot wire material produced at comparable temperatures. To study the stability of these films, an optimised degradation method was developed in which a pulsed dye laser was used in combination with a monochromatic steady beam to achieve a relatively fast stabilisation of the light induced degradation. The film quality was monitored by the photoconductivity and by the ambipolar diffusion length from which the material parameter, <i>μ</i>⁰<i>τ</i>⁰, was extracted. Taking into account the transport properties after light soaking as well as the optical absorption we concluded that the hot wire material could lead to more stable solar cells in comparison with plasma enhanced chemical vapor deposition material.