If you read about any expansion of solar cell manufacturers these days, it is mostly about equipment they order for PERC cells. Only on April 7, leading Chinese cell maker JA Solar ordered production tools for PERC cells (and some other machines) that can process a volume of 1.5 GW (see article Meyer Burger bags 18 mn CHF order).
PERC stands for Passivated Emitter Rear Cell and is an advanced silicon cell architecture that comes with a promise of higher efficiencies. At the same time, it requires only minimal changes to existing solar cell processing lines. The concept is not new; it was invented in 1983 by well known Australian scientist Martin Green, but is now being implemented on a large scale.
My colleague Shravan Chunduri and me have delved deep into PERC technology and published an in-depth report – “PERC Solar Cell Technology 2016 – Background, Status and Outlook”, which can be downloaded free of charge (see link below).
Opting for PERC means to add a rear passivation scheme to standard BSF cell technology. As for the implementation, it involves depositing a rear surface passivation film, which is subsequently opened to give way for formation of a rear contact. In addition, the chemical wet-bench based edge-isolation step is tweaked for rear polishing. The key aspect of PERC technology is to deposit the rear passivation film.
Proven equipment available
As for the rear passivation material of choice, silicon oxynitride was used in the early days of PERC development, and cell makers, like SolarWorld, have used it for commercial production. In the meantime, aluminum oxide has taken over as the dominating material for rear passivation – and here you can use “solar-proven” PECVD equipment as well as ALD machines for deposition.In our study, we present an overview of the leading equipment suppliers.
Efficiencies are quickly improving for PERC cells. Currently, Trina holds the world record for monocrystalline PERC at 22.13% efficiency.
Challenges can be managed
Like any other technology, PERC faces challenges. Additional investments required to add machinery or to start new lines, product bankability, data supporting the long term reliability of aluminum oxide, stable operation of production tools are teething problems. The industry is supposed to overcome these issues as it gains more experience using the technology. The major concern is the so-called Light Induced Degradation (LID) effect, which is especially associated with multicrystalline PERC cells today. LID can cause module power losses of up to 10%. Its root cause is not completely understood. However, the first companies – QCells and REC – say they have found the remedy and have started mass production of multicrystalline PERC cells.
While there are other competing high-efficiency cell technologies at which we are looking our report, for us it is clear that PERC is absolutely ready for prime time. We estimate that 4.9 GW of PERC capacity was installed in 2015, resulting in about 3 GW of PERC cell production. In 2016, the cumulative production capacity could reach 11.8 GW, and 8.1 GW PERC products could hit the market. And this is only the beginning.
You can download the study “PERC Solar Cell Technology 2016 – Background, Status and Outlook” free of charge here: