Silicon Heterojunction Solar Cells with Open-Circuit-Voltage above 750mV

In this paper we present silicon heterojunction (SHJ) cells with Voc beyond 750mV fabricated on thin wafers on a semi-industrial pilot line. Once critical parameters for SHJ cell are insured, such as very high quality n-Cz material (2 Ohm.cm – 8ms typically), good wet cleaning along with right queue-time conditions, good PECVD a-Si:H passivation (Seff <2 cm/s typically) and limited damage induced during ITO deposition and screen printing, the recipe development is not a first order work. The most important point is to insure cell processing below 90μm without extra defectivity. This was done in this work thanks to specific know how and practical adjustment of automation, handling, logistics of thin cells (40 to 90μm free standing 156x156 mm2 wafers). The best Voc of this work is 752mV and 751mV independently measured by ISFH-CalTeC on total area 244.3 cm2 (M2 size), bifacial, rear emitter, 4 busbar cells. Accordingly, <1 g Si/Wp was acheived with a record at 0.52 g Si/Wp for a 44μm cell. Very promising implied Voc up to 765mV on cell precursors post PECVD and losses analysis show possible cell Voc >755mV and a <0.5 g Si/Wp figure of merite short term.