Faculté des sciences

Determination of the quality of a-Si:H films: “true”transport parameters

Beck, N. ; Shah, Arvind ; Wyrsch, Nicolas

In: Conference Record of the Twenty Fourth IEEE Photovoltaic Specialists Conference (1994 IEEE First World Conference on Photovoltaic Energy Conversion), 1994, vol. 1, p. 476-479

For the characterisation of a-Si:H layers, steady-state photoconductivity (SSPC) and steady-state photocarrier grating (SSPG) are currently used. But the μτ-products deduced from these measurements are a function of the prevailing dangling bond occupation in the film and, thus, are not a measure of material quality. In the present paper the authors introduce the product... Plus

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    Summary
    For the characterisation of a-Si:H layers, steady-state photoconductivity (SSPC) and steady-state photocarrier grating (SSPG) are currently used. But the μτ-products deduced from these measurements are a function of the prevailing dangling bond occupation in the film and, thus, are not a measure of material quality. In the present paper the authors introduce the product μ0τ0, which is independent of dangling bond charge and which monitors material quality in terms of band mobility μ0 and capture time τ0, the latter being, in its turn, inversely proportional to dangling bond density. They present a simple evaluation procedure to deduce μ0τ0 from simultaneously performed SSPC and SSPG measurements. In undoped, but slightly n-type a-Si:H, the quality of the material will typically be related to the ambipolar diffusion length rather than to photoconductivity. The application of this method to a series of undoped a-Si:H films and solar cells incorporating these materials exhibited a good correlation between film properties and cell performances.