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Combining market-proven silicon solar cell technology with an efficient wide band gap top cell into a tandem device is an attractive approach to reduce the cost of photovoltaic systems. For this, perovskite solar cells are promising high-efficiency top cell candidates, but their typical device size (<0.2 cm 2 ), is still far from standard industrial sizes. We present a 1 cm 2 near-infrared transparent perovskite solar cell with 14.5% steadystate efficiency, as compared to 16.4% on 0.25 cm 2 . By mechanically stacking these cells with silicon heterojunction cells, we experimentally demonstrate a 4-terminal tandem measurement with a steady-state efficiency of 25.2%, with a 0.25 cm 2 top cell. The developed top cell processing methods enable the fabrication of a 20.5% efficient and 1.43 cm 2 large monolithic perovskite/silicon heterojunction tandem solar cell, featuring a rear-side textured bottom cell to increase its near-infrared spectral response. Finally, we compare both tandem configurations to identify efficiency-limiting factors and discuss the potential for further performance improvement.

As highlighted by recent conversion efficiency records, passivating contacts are keys to fully exploit the potential of crystalline silicon as a light absorbing semiconductor. Prime passivating contact technologies include a-Si/c-Si silicon heterojunctions and high temperature tunnel oxide/polysilicon-based contacts. The first has the advantage of a simple fabrication process, but it is incompatible with standard metallization processes and bulk semiconductor defect treatments which take place at temperature > 800°C. The second relies on a buried junction or dopant profile near the tunnel oxide, and requires process times of several minutes at high temperature. In this paper, we solve the scientific question to know whether such a dopant profiles, with the possible the presence of nano-holes, is required to make an efficient contact when using a tunnel oxide. We show that, by leveraging the versatility of plasma deposition processes, it is possible to realize Si-based thin-film doped layers that withstand a short annealing at high temperature (> 800 for typ 10 s, called "firing"), passivate the c-Si interface and foster collection of photo-generated charge carriers by inducing a strong electric field at the Si-surface near the interface with SiOx. The contact has a high-compatibility with existing industrial process: a plasma deposition of a thin-film layer at the rear side followed by a rapid thermal treatment ("firing"), an essential process for metallization formation of industrial cells. With the developed technology, we fabricated proof-of-concept p-type solar cells with conversion efficiency up to 21.9%.

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We present a novel passivating contact structure based on a nanostructured siliconbased layer. Traditional poly-Si junctions feature excellent junction characteristics but their optical absorption induces current losses when applied to the solar cell front side. Targeting enhanced transparency, the poly-Si layer is replaced with a double-layer stack consisting of a nanostructured silicon oxide capped with a nanocrystalline silicon (nc-Si) layer. The nanostructured silicon oxide layer consists of an amorphous SiOx matrix with incorporated Si filaments connecting one side of the layer to the other, and is referred to as nanocrystalline silicon oxide (nc-SiOx) layer. We investigate passivation quality, measured as saturation current density, and nanostructural changes, characterized by Raman spectroscopy and transmission electron microscopy, carefully studying the influence of annealing dwell temperature. Excellent surface passivation on n-type and also p-type wafers is shown. An optimum annealing temperature of 950 °C is found, resulting in a saturation current density of 8.8 fA cm-2 and 11.0 fA cm-2 for n-type and p-type wafers, respectively. Efficient current extraction is presented with specific contact resistivities of 86 mΩ cm 2 on n-type wafer and 19 mΩ cm 2 on p-type wafers, respectively. Highresolution transmission electron microscopy reveals that the layer stack consists of intermixed SiOx and Si phases with the Si phases being partly crystalline already in the asdeposited state. Thermal annealing at temperatures ≥ 850 °C further promotes crystallization of the Si-rich regions. We show that the addition of the SiOx phase enhances the thermal stability of the contact and we expect it to allow to tune the refractive index and improve transparency while still providing efficient electrical transport thanks to the crystalline Si phase, which extends throughout almost the entire layer.