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International audience; This work explores the possibility to use the mechanism of hopping conduction – and particularly the transition temperature between band and hopping conduction – on low temperature resistivity measurements, for the control of dopants densities in p‐type compensated silicon. This work first establishes a parametric study of the hopping conductivity: the impact of the majority dopant density and of the compensation ratio is investigated. In the range of majority dopant concentration studied (5×1016 cm–3–5×1017 cm–3), a linear relation seems to appear between the majority dopant concentration and the transition temperature, and this, apparently whatever the compensation impurity type or the crystalline structure. It was then shown that both minority and majority dopant densities can be estimated from a single resistivity versus temperature curve. To our knowledge, this work presents the first experimental study of the feasibility of using such mechanisms to collect relevant information on the compensated Si composition.

We studied the influence of copper (Cu) on the performances of conventional photovoltaic (PV) solar cells by growing two multicrystalline (mc) boron-doped silicon (Si) ingots from ultra-pure feedstocks, one of these feedstocks being deliberately contaminated with 90 ppm wt of Cu. Industrial-like solar cells were fabricated and the associated external gettering and hydrogenation effects were studied. An originality of our approach consisted in evaluating the forward but also reverse current-voltage (I-V) characteristics of the fabricated cells. Furthermore we assessed the stability under illumination of the PV parameters as Cu is known to be responsible for light-induced degradations (LID) of the carrier lifetime. On the one hand we unexpectedly showed that the PV conversion efficiency (η) was not affected by the initially large Cu concentrations. We demonstrated that it was due to the complementary actions of the external gettering effect developed by the phosphorus-diffusion and the bulk hydrogenation. The Cu-addition slightly enhanced the pn junction hard breakdown, however the extracted junction breakdown voltages fulfilled the common industrial requirements for this parameter. On the other hand we highlighted significant decreases under illumination of the PV performances for the Cu-contaminated solar cells fabricated from wafers coming from the upper part of the ingot (i.e., samples with the highest Cu concentration). These decreases could be explained by the previously proposed mechanisms in the literature, which argue that the excess charge carriers could reduce the electrostatic repulsion between interstitial Cu ions and Cu precipitates, this effect enhancing the Cu precipitation. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)