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%.

We present an electron selective passivating contact based on a tunneling SiO x capped with a phosphorous doped silicon carbide and prepared with a high-temperature thermal anneal. We investigate in detail the effects of the preparation conditions of the SiC x (n) (i.e., gas flow precursor and annealing temperature) on the interface recombination rate, dopant in-diffusion, and optical properties using test structures and solar cells. On test structures, our investigation reveals that the samples annealed at temperatures of 800-850°C exhibit an increased surface passivation toward higher gas flow ratio (r = CH 4 /(SiH 4 + CH 4)). On textured and planar samples, we obtained best implied open-circuit voltages (i-V O C) of 737 and 746 mV, respectively, with corresponding dark saturation current densities (J 0) of ∼8 and ∼4 fA/cm 2. The SiC x (n) layers with different r values were applied on the textured front side of p-type c-Si solar cells in combination with a borondoped SiC x (p) as rear hole selective passivating contact. Our cell results show a tradeoff between V O C and short-circuit current density (J S C) dictated by the C-content in the front-side SiC x (n). On p-type wafers, best V O C = 706 mV, FF = 80.2%, and J S C = 38.0 mA/cm 2 with a final conversion efficiency of 21.5% are demonstrated for 2 × 2 cm 2 screen-printed cells, with a simple and patterning-free process based on plasma depositions and one annealing step 800°C < T < 850°C for the formation of both passivating contacts.

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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