High-Efficiency Industrial PERC Solar Cells for Monofacial and Bifacial Applications

Abstract

The passivated emitter and rear cell (PERC) concept is currently rapidly being introduced into industrial mass production and is expected to be the new silicon wafer based solar cell technology standard in the photovoltaics industry. In 2018, PERC-type solar cells accounted for approximately 40% of the worldwide produced solar cells and their share is expected to rapidly increase up to 70% within the next few years. Compared to the previous industrial silicon solar cell technology which applied a full-area aluminum rear contact, PERC cells passivate the rear silicon wafer surface with a dielectric layer and only locally contact the silicon wafer with an aluminum metal contact, which reduces charge carrier recombination and hence increases the conversion efficiency. Present record conversion efficiencies up to 22.8% of industrial PERC cells hence exceed the efficiency of conventional Al-BSF silicon solar cells by more than 2%abs. In addition, PERC solar cells can be made bifacial by substituting the full-area rear aluminum layer with an aluminum finger grid design. This so-called PERC+ solar cell design enables large volume industrial manufacturing of bifacial silicon solar cells which absorb stray light from the rear side and hence increase the energy yield by 5–25% depending on the detailed module installation conditions. This chapter describes the most important research results and technology developments of the past decades as well as the present status of industrial PERC and PERC+ solar cells.