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• Blister-free boron-doped poly-Si layers are obtained by PECVD through optimization of the deposition temperature and gas ratio. • The process developed is approaching the industrial standards (large area KOH-polished wafers, SiOx growth included in standard RCA cleaning, semi-industrial PECVD tool). • High and homogeneous surface passivation properties are obtained (iVoc = 734 mV and J0 = 7 fA•cm-2). • Conductive spots detected by C-AFM are not mirroring pinholes within the interfacial SiOx layer.

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Influence of substitutional metallic impurities on the performances of p -type crystalline silicon solar cells: The case of gold Doping dependence of the carrier lifetime crossover point upon dissociation of iron-boron pairs in crystalline silicon Appl.

This letter focuses on the evolution under illumination of the carrier lifetime in n-type boron–phosphorus compensated Czochralski silicon. Our results show a Light-Induced-Degradation (LID) of the carrier lifetime which we prove to be related to additional boron. The activation energy of the annihilation mechanism for this boron-related defect was found to be 1.7 eV, in agreement with values concerning the annihilation of the BOi2 complex responsible for the LID of boron-doped p-type silicon. This strongly suggests that BOi2 are also responsible for the degradation of n-type boron–phosphorus compensated silicon unlike what was expected from previous studies on compensated p-type silicon.

This letter focuses on the kinetics of the light-induced-degradation in multicrystalline silicon, comparing electronic grade and strongly compensated solar-grade materials. In electronic grade material, the results fit well with the models developed for Czochralski grown single-crystals. In contrast, in solar grade material, the light-induced-degradation kinetics are much slower and cannot be described by the existing models. We discuss how the formation of boron-oxygen complexes may be altered by the effects of compensation.The production of low cost silicon ͑Si͒ purified by metallurgical routes is identified as an important cost-reduction opportunity for the photovoltaic industry. Due to the difficulty of removing dopants, this Si is often compensated. This letter shows that the kinetics of the light-induced-degradation ͑LID͒ in compensated solar-grade ͑SoG͒ multicrystalline Si ͑mc-Si͒ are strongly different from those observed in electronic-grade ͑EG͒ materials.LID is due to the formation under illumination of complexes associating boron ͑B͒ and oxygen ͑O͒ atoms that enhance carrier recombination. 1,2 In EG Czochralski ͑Cz͒ grown single crystals ͑sc-Si͒, it has been shown that LID occurs in two distinct and independent steps: a fast process reaching completion on a time scale of tens of seconds, followed by a slow process lasting several hours. 3 It has been proposed that the slow process is characterized by the diffusion of a mobile positively charged O dimer ͑O i2 ͒ toward a negatively charged substitutional B atom. 2 The O i2 diffusion takes place via a Bourgoin-Corbett mechanism, which involves changes in the structure of the O i2 by alternately capturing an electron and a hole. 4 For uncompensated EG Cz-Si, Palmer et al. 5 proposed a model to describe the reaction kinetics of this slow process, which is in excellent agreement with experimental data. We will show that this model can also be used to describe the LID in uncompensated EG mc-Si but fails for compensated SoG Si, in which we find the LID kinetics to be much slower and to follow different scaling laws. We will propose possible reasons for such discrepancies.From the measured open circuit voltage ͑V oc ͒ values under illumination, for uncompensated Cz-Si solar cells, a normalized concentration ͑N ‫ء‬ ͒ of the illumination-induced defects can be defined as 5Previous studies of the LID showed that in uncompensated Cz-Si, N ‫ء‬ ͑T , t͒ experimental results can be represented by an expression of the formwhere R gen is the generation rate of the complex. The validity of the form given by Eq. ͑2͒ has been theoretically confirmed by Palmer et al., 5 who also proposed for R gen the following expression:p is the hole concentration, h is the hole thermal velocity ͑equal to 1.675ϫ 10 7 cm s −1 ͒, N Si is the Si atomic density, h is the hole-capture cross section of O i2 , and ␥ is the number of sites around B s , which when reached by O i2 causes the automatic formation of the BO i2 complex. The value of ␥ has been derived by Palmer et al. 5 through a captur...

Compensation effects are intensively studied on two highly doped ingots grown from solar-grade silicon feedstocks purified using metallurgical routes, through a comparison of the electrical properties at iso-carrier densities. Working at given carrier densities enables a clearer extraction of the compensation effects, at the wafer and solar cell levels. At the wafer level, the majority carrier mobility and the carrier lifetime are investigated. Regarding the mobilities, it was found that current models may underestimate the amount of incomplete ionization of boron leading to underestimated mobilities. In addition, the majority carrier mobility was found to be strongly affected at high compensation level. Regarding the carrier lifetimes, our results show that after a phosphorus diffusion step, dopants alone — and especially boron — can limit the lifetime in highly doped solar-grade silicon. At the cell level, I-V characteristics under standard illumination were studied. In particular, the observed reductions in short-circuit current on solar cells having a very high compensation level could be explained in terms of a compensation-induced reduction in the minority carrier mobility. We also report high conversion efficiencies of up to 15.9% on solar cells showing a boron content greater than two ppmw (2.6 × 1017 cm−3), which is generally considered unsuitable for solar cell manufacturing.