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37th European Photovoltaic Solar Energy Conference and Exhibition; 233-237, We investigate a commercially feasible roadmap towards 24% efficient PERC cells in mass production based on low cost screen printing and tube diffusion and passivation technology. We do this through (i) the fine-tuning of our process and device design, which resulted in 23.39% efficient PERC cells on Ga-doped CZ wafers, independently confirmed by ISFH CalTeC; and (ii) state-of-art device simulations, based on monitor wafers and finished cell measurements, to forecast changes in process and device design. We compare our results with the well-known PERC roadmap of Min et al. and discuss, in which details commercial production differs nowadays from the forecast of this well-known road map made 5 years ago. The differences are a better understanding of hydrogenation, an improved low-pressure phosphorus diffusion, and Ga-doped wafers. The improvements of these three features in mass production make it likely that, in contrast to the forecast five years ago, close to 24% efficiency may be obtained even without advanced printing techniques. This makes it likely that the standard PERC cells keeps in mainstream for another about 3 years before passivating contacts take over.

36th European Photovoltaic Solar Energy Conference and Exhibition; 294-299, Over the decades, photovoltaics laboratories and industry have worked intensely to improve the silicon solar cell efficiency to approach the theoretical limit, by demonstration of a champion cell and by industrialization of such cell concepts. There are several well-known cell concepts that have been successful both in academia and in GW scale production, like the Passivated Emitter and Rear cell (PERC), the heterojunction with intrinsic thin-layer (HIT) cell or heterojunction technology (HJT) cell, and the interdigitated back contact (IBC) cell. This poses the question of how to further improve the industrial cell efficiency to over 25% with reasonable cost. In this paper, we review the latest champion cells developed by different institutes or companies, and we find that some new hybrid bifacial solar cells with passivating contacts (via intrinsic a-Si/doped a-Si, or tunnel SiOx/doped poly Si) can be potentially new areas to focus on. An efficiency drop of about 1%abs from the best champion cell to mass production median efficiency at that time is observed. In the second part of the paper, we report on the mass production of our new largearea bifacial i-TOPCon (industrial tunnel oxide passivating contact) cells with an average front side efficiency over 23%, and a champion laboratory cell with 24.58%, confirmed by ISFH CalTeC. The champion large-area screenprinted IBC cell, passivated with SiOx/n-poly, reaches an efficiency of 25.04%, confirmed by JET. Our double glass bifacial modules, consisting of 60 pcs of 161.7 mm i-TOPCon cells, have a standard power over 350 Wp. Finally, an overall gain of 6.5% of our bifacial modules is demonstrated by a direct and fair comparison with other modules in a 100 kW system installed over a lake in Changzhou and monitored over two years.

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International audience; Focused ion beam technique is a powerful tool for defining patterns within a semiconductor film. In this paper, we show that it is possible to realize patterns such as disks and columns within thick GaN templates and that it is compatible with the regrowth of GaN based heterostructures. We study the effect of the pattern size and shape on the regrowth by molecular beam epitaxy. We show that the growth using ammonia as the nitrogen source with flux at temperature optimized for 2-dimensional growth leads to the apparition of well defined growth planes. We show that the development of these planes is dependent with the initial pattern size and shape. These results confirm the difficulty for realizing micro or nano-columns with axial heterostructures. At the opposite, these growth conditions seem favourable for core-shell heterostructures column with well defined m-plane and eventually a-plane lateral facets