• 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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Passivating the contacts of crystalline silicon (c-Si) solar cells (SC) with a poly-crystalline silicon (poly-Si) layer on top of a thin silicon oxide (SiOx) is currently sparking interest for reducing carrier recombination at the interface between the metal electrode and the c-Si substrate. However, due to the interrelation between different mechanisms at play, a comprehensive understanding of the surface passivation provided by the poly-Si/SiOx contact in the final SC has not been achieved yet. In the present work, we report on an original ex-situ doping process of the poly-Si layer through the deposition of a B-rich dielectric layer followed by an annealing step to diffuse B dopants in the layer. We propose an in-depth investigation of the passivation scheme of the resulting B-doped poly-Si/SiOx contact by first comparing the surface passivation provided by ex-situ doped and intrinsic poly-Si/SiOx contacts at different steps of the fabrication process. The excellent surface passivation properties obtained with the ex-situ doped poly-Si(B) contact (iVoc = 733 mV and J0 = 6.1 fA cm -2 ) attests to the good quality of this contact. We then propose further STEM, ECV and ToF-SIMS characterizations to assess: i) the evolution of the microstructure and

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Passivating the contacts of crystalline silicon (c‐Si) solar cells with a poly‐crystalline silicon (poly Si) layer on top of a thin silicon oxide (SiOx) film are currently of growing interest to reduce recombination at the interface between the metal electrode and the c‐Si substrate. This study focuses on the development of boron‐doped poly‐Si/SiOx structure to obtain a hole selective passivated contact with a reduced recombination current density and a high photo‐voltage potential. The poly‐Si layer is obtained by depositing a hydrogen‐rich amorphous silicon layer by plasma enhanced chemical vapor deposition (PECVD) exposed then to an annealing step. Using the PECVD route enables to single side deposit the poly Si layer, however, a blistering of the layer appears due to its high hydrogen content, which leads to the degradation of the poly‐Si layer after annealing. In this study, the deposition temperature and gas flow ratio used during PECVD step are optimized to obtain blister‐free poly‐Si layer. The stability of the surface passivation properties over time is shown to depend on the blister density. The surface passivation properties are further improved thanks to a post process hydrogenation step. As a result, a mean implied photo‐voltage value of 714 mV is obtained.

International audienceThis work deals with the understanding of the transport behavior of different deposited Indium Tin Oxide (ITO) layers on the emitter of n-type heterojunction solar cells. A complete study based on effective lifetime measurements has been carried out on samples with different ITO thicknesses to evaluate the passivation quality before and after ITO deposition, showing that increasing the ITO thickness degrades the passivation properties only at low injection level. Further characterizations coupled with numerical simulations demonstrate that such a behavior is due to recombination at the ITO/(p) a-Si:H interface induced by the ITO layer

The use of ion implantation for PV application could be an innovative way of developing advanced cell structures with respect to a very simple fabrication process. Its application on p-type silicon solar cells has already showed its potential with the achievement of efficiency above 19% with selective emitter structure [1]. Nevertheless, the development of more complexes architectures like the ntype boron emitter is even more promising as the fabrication process would remain simple and the cell efficiency could be significantly improved. This study is dedicated to the achievement of high quality boron implanted emitter on textured surface. Very low emitter saturation current densities (J0e) of 80fA/cm² with implied Voc of 665mV were reached. The influence of the thermal treatment was also investigated for P-implantation. Large area solar cells (148.6cm²) on n-type Cz substrates were fabricated by co-annealing boron emitter and phosphorous BSF respectively at the front and back side of the cell. This fabrication process only requires nine processing steps which lead to a much simpler process than the conventional one made by means of single side gas diffusion. Finally, efficiencies of 16.9% were obtained with relatively poor open-circuit voltage and short-circuit current. Detailed characterization indicates a poor emitter quality which is not consistent with the saturation current density obtained on symmetrical samples. The impact of the thermal budget on the electrical properties of the wafers was investigated.