Intense Pulsed Light Meets the Metallization of Silicon Heterojunction Solar Cells

Intense pulsed light (IPL) is investigated as an extremely fast alternative contact formation process for silicon heterojunction (SHJ) solar cells. On non-metallized samples, it is proven that IPL is compatible with the temperature-sensitive heterojunction structure. Indeed, SHJ samples’ initial implied open-circuit voltage of 715 ± 2.9 mV is increased by 25.9 ± 2.3 mV using IPL processing while the thermal curing results in an improvement of only 20.4 ± 2.2 mV. Furthermore, selected SHJ-compatible IPL processes are applied on inkjet- and screenprinted test structures, enabling a minimal mean finger resistance Rf of 3.0 ± 0.7 Ω/cm. Simultaneously, a contact resistivity ρC of 2.7 ± 0.2 mΩ∙cm² is achieved utilizing a commercially available, silver-coated copper paste for screen printing. Finally, busbarless bifacial SHJ solar cells are manufactured substituting the conventional thermal curing with IPL processing. A median conversion efficiency of 22.5% is achieved with both-sides IPL-processed SHJ solar cells exhibiting silver-coated copper-based grids that outperform the thermally treated cells by 0.2%abs. Since flashes of light with a pulse length in the millisecond range are utilized, IPL allows for a significant decrease of overall process time and footprint.