‘Solar Module Super League’ (SMSL) member, Trina Solar has set a conversion efficiency record of 24.58% for an i-TOPCon (Industrial Tunnel Oxide Passivated Contact) bifacial solar cell using a super-sized 244.62 cm2 wafer.
Today’s industry standard B-doped monocrystalline silicon still suffers from light-induced degradation of the carrier lifetime. Illumination at elevated temperature leads to a so-called regeneration, i.e. a recovery of the carrier lifetime as well as the solar cell efficiency. However, even though the carrier lifetime on test wafers increases from about 1 ms after processing to 3 ms after regeneration, the corresponding PERC+ cell efficiencies in both states are identical. We discuss possible reasons for this discrepancy. Additionally, we evaluate B-doped Czochralski silicon wafers with an ultra-low oxygen content of 2.6 ppma as well as industrial Ga-doped wafers. Both wafer materials are completely LID-free in lifetime measurements and PERC+ cell efficiencies and enable up to 0.4%abs higher efficiencies than present industry-typical boron-doped wafers.
The Institute for Solar Energy Research Hamelin (ISFH) and the Leibniz Universität Hannover have produced lab cells using polysilicon on oxide – POLO – junctions, in an interdigitated pattern on the rear side and a specially treated p-type monocrystalline wafer to record a cell conversion efficiency of 26.1%.
Finlay Colville talks to Linda Koschier and Stuart Wenham about University of New South Wales (UNSW) alumni having prominent solar cell industry positions and technology issues such as advanced hydrogenation,
Passivated emitter and rear cell (PERC) technology has been forecast to become mainstream in the next few years, gaining around a 30% market share. This paper presents a novel PERC solar cell design in which a screen-printed rear aluminium (Al) finger grid is used instead of the conventional full-area Al rear layer, while implementing the same PERC manufacturing sequence. This novel cell concept, called ‘PERC+’, offers several advantages over PERC, explored in the paper.