High-temperature passivating contact

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 %.

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.

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