Determination of the quality of a-Si:H films: “true”transport parameters
Date de parution
Conference Record of the Twenty Fourth IEEE Photovoltaic Specialists Conference (1994 IEEE First World Conference on Photovoltaic Energy Conversion), Institute of Electrical and Electronics Engineers (IEEE), 1994/1//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 μ<sup>0</sup>τ<sup>0</sup>, which is independent of dangling bond charge and which monitors material quality in terms of band mobility μ<sup>0</sup> and capture time τ<sup>0</sup>, the latter being, in its turn, inversely proportional to dangling bond density. They present a simple evaluation procedure to deduce μ<sup>0</sup>τ<sup>0</sup> 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.
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