High-temperature passivating contact

High-efficiency crystalline silicon solar cells cannot be achieved without excellent electrical contacts. The trade-off between high performance contact and low processing complexity is however a major challenge in the manufacturing of solar cells. The high-temperature passivating contact group of PVlab is aiming at bringing innovative processes to achieve mitigation of metal recombination. Advanced characterization techniques are also a key research activity in order to understand the structural and chemical structure of such contacts.

Firing compatible passivating contact (FPC)

Passivating contacts are indispensable for achieving high conversion efficiency in crystalline-silicon solar cells. Their realization and integration into a convenient process flow have become crucial research objectives. To this aim we developed an alternative passivating contact that is formed in a single post-deposition annealing step called ‘firing’, an essential step for current solar cell manufacturing. The integration of the FPC as rear hole selective contact, co-fired with a screen-printed Ag-grid contacting a POCl3 diffused front emitter, resulted in a conversion efficiency above 22 %.

Front and rear contacted solar cells with passivating contacts

To fully mitigate metal recombination losses on the front and rear side while using a simple fabrication process, we developed passivating contact for front and rear contacted solar cells. Electron- and hole-selective passivating contacts based on in-situ doped silicon carbide (SiCx) deposited by plasma enhanced chemical vapor deposition were optimized. Their potential is demonstrated in solar cells processed with a simple process flow, in which the junction formation of the two polarities is achieved with a single co annealing step. Planar p-type cells reach a fill factor of 83.4% and an open-circuit voltage of 726 mV. By realizing front-side-textured and rear-side-planar p-type cells, an efficiency of up to 22.6% is achieved.

Advanced characterization of passivating contacts

Several characterization techniques (FTIR, Raman, XRD, EDX and SIMS) are extensively used to evaluate the structural and chemical composition of the fabricated passivating contacts.

Interactions between aluminium and fired passivating contacts during fire-through metallization (vol 249, 112051, 2023)

S. Libraro; M. Lehmann; J. J. D. Leon; C. Allebe; A. Descoeudres et al. 

Solar Energy Materials And Solar Cells. 2024-02-06. Vol. 267, p. 112722. DOI : 10.1016/j.solmat.2024.112722.

Font Side Solutions for c-Si Solar Cells with High-Temperature Passivating Contacts

E. Genç / F-J. Haug; C. Ballif (Dir.)  

Lausanne, EPFL, 2024. 

Microstructural and electrical characterization of high temperature passivating contacts for silicon solar cells

S. Libraro / A. Hessler-Wyser; F-J. Haug (Dir.)  

Lausanne, EPFL, 2024. 

Rear textured p-type high temperature passivating contacts and their implementation in perovskite/silicon tandem cells

A. Walter; B. A. Kamino; S-J. Moon; P. Wyss; J. J. D. Leon et al. 

Energy Advances. 2023-11-09. Vol. 2, num. 11, p. 1818-1822. DOI : 10.1039/d3ya00048f.

Understanding and mitigating resistive losses in fired passivating contacts: role of the interfaces and optimization of the thermal budget

S. Libraro; A. M. I. Morisset; J. Hurni; E. Genc; L. Antognini et al. 

Solar Energy Materials And Solar Cells. 2023-10-11. Vol. 263, p. 112591. DOI : 10.1016/j.solmat.2023.112591.