Heraeus achieves 21.2% record efficiency with metallization pastes

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Germany’s Institute for Solar Energy Research Hamelin (ISFH) has increased the conversion efficiency of industrial p–type silicon solar cells with screen-printed metal contacts from the current average of 17.5% to 19.5% to a record value of 21.2% using front-side metallization pastes supplied by Heraeus Precious Metals’ Photovoltaics Business Unit.

Heraeus said 21.2% — a measurement confirmed by the independent institute Fraunhofer ISE CalLab — was the highest efficiency reported so far for industry typical silicon solar cells using screen-printed metal contacts.

The company added that a combination of different technologies enabled the impressive result on an industrial passive emitter rear cell (PERC). As opposed to conventional cells, PERC cells have a passivated rear-side, which increases the amount of energy captured from the cell. ISFH’s cell design incorporates a narrow front-side grid design using a dual printing process and an advanced five busbar design. The special layout enables the reduction of finger line widths to 46 micrometres, which decreases shadowing losses and serial resistance.

The narrower finger lines were printed with Heraeus’ front-side silver metallization paste that processes a high fill factor and low series resistance. The busbars were printed using Heraeus’ newest low activity paste.

"A 21.2% conversion efficiency for a PERC cell using standard production equipment is a true breakthrough,” said Weiming Zhang, vice president of technology at Heraeus’ Photovoltaics Business Unit.

“With the excellent processing knowledge and solar cell expertise of the ISFH, the front-side silver-pastes of Heraeus unfolded their cells’ peak performance. Cooperation with partners within the PV industry such as the ISFH is essential for us. It’s an ideal platform to exchange state-of-the-art knowledge in cell technology and processing know-how for advancing solar energy."