Beyond boron-oxygen-deactivation: industrial feasible LID-free p-type Czochralski silicon

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.

ISFH pushes p-type mono cell to record 26.1% conversion efficiency

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%.

The PERC+ cell: More output power for less aluminium paste

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.