Providing state-of-the-art surface passivation and the required carrier selectivity for both contacts, hydrogenated amorphous silicon thin films are the key components of silicon heterojunction (SHJ) solar cells. After intensive optimization of these layers for standard front and back contacted (FBC) n-type cells, high surface passivation levels were achieved on cell precursors, demonstrated by minority carrier lifetimes exceeding 18 ms on float-zone (FZ) and 11 ms on Czochralski (Cz) c-Si wafers. The application of these very same layers on cheaper and commercially available Cz ptype wafers resulted in similar passivation quality, with lifetimes above 10 ms as well.Large-area industrial bifacial FBC SHJ cells processed on wafers taken along the full length of a high-resistivity Cz p-type ingot showed efficiencies in the 22.5% to 23% range, significantly higher than previously reported results on such substrates and on par with their n-type counterparts. Best efficiencies on large-area monofacial devices (>220 cm 2 ) are 23.6% on Cz p-type and 24.4% on Cz n-type, similar to certified results obtained on lab-scale cells (4 cm 2 ), 23.76% on FZ p-type and 24.21% on FZ n-type. Notably, no specific adaptation of the reference n-type cell process was necessary to achieve these results on p-type material. Additionally, a 25% certified efficiency has been obtained on medium-sized (25 cm 2 ) interdigitated backcontacted SHJ cells, featuring the same passivation layers developed for FBC devices.These results illustrate the versatility of the SHJ technology for various highefficiency screen-printed solar cell configurations and show possible ways to improve its competitiveness on the global photovoltaic market.

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In this article we investigate the effect of prolonged light exposure on silicon heterojunction solar cells. We show that although light exposure systematically improves solar cell efficiency in the case of devices using intrinsic and p-type layers with optimal thickness, this treatment leads to performance degradation for devices with an insufficiently thick (p) layer on the light-incoming side. Our results indicate that this degradation is caused by a diminution of the (i/p)layer stack hole-selectivity due to light exposure. Degradation is avoided when a sufficiently thick (p) layer is used, or when exposure of the (p) layer to UV light is avoided, as is the case of the rear-junction configuration, commonly used in industry. Additionally, applying a forward bias current or an infrared light exposure results in an efficiency increase for all investigated solar cells, independently of the (p) layer thickness, confirming the beneficial influence of recombination on the performance of silicon heterojunction solar cells.

The window-layer stack limits the efficiency of both-side-contacted silicon heterojunction solar cells. We discuss here the combination of several modifications to this stack to improve its optoelectronic performance. These include the introduction of a nanocrystalline silicon-oxide p-type layer in lieu of the amorphous silicon p-type layer, replacing indium tin oxide with a zirconium-doped indium oxide for the front transparent electrode, capping this layer with a silicon-oxide film, and applying a post-fabrication electrical biasing treatment. The influence of each of these alterations is discussed, as well as their interactions. Combining all of them finally enables the fabrication of a highly transparent and electrically well-performing windowlayer stack, leading to a screen-printed silicon heterojunction solar cell with 24.1% efficiency. Paths towards industrialization and for further improvements are finally discussed.