The Passivated Emitter and Rear Cell (PERC): From conception to mass production

Improved solar cell efficiency is the key to ongoing photovoltaic cost reduction, particularly as economies of scale propel module-manufacturing costs towards largely immutable basic material costs and as installation costs become an increasingly large contributor to total system costs. To enable manufacturers to move past the 20% cell energy conversion efficiency figure in production, high-efficiency PERC (Passivated Emitter and Rear Cell) sequences are being increasingly brought online. Most new photovoltaic manufacturing capacity added in the second half of 2014 was PERC-based, making PERC now the cell technology with second-highest production capacity, with the latest industry roadmap anticipating PERC will become the dominant commercial cell technology by 2020. The first paper describing the PERC cell appeared in 1989, although the structure was conceived several years earlier. The attractive technical features were the reduction of rear surface recombination by a combination of dielectric surface passivation and reduced metal/semiconductor contact area while simultaneously increasing rear surface reflection by use of a dielectrically displaced rear metal reflector. The key issues in the development of this technology and its commercial implementation are described, including a review of recent adoption rates and the way these are likely to evolve in the future.