Review and Highlights of More Than 30 Years Research on Ever Improving Technology for PERC Solar Cells at Fraunhofer ISE

The transition of the passivated emitter and rear cell (PERC) from laboratory to industrial production is one of the most important chapters in photovoltaic (PV) technology. PERC-based technologies started to dominate the PV industry in 2018. However, considering the long-time span between the first laboratory prototypes in 1984, the introduction in industrial pilot lines in 2011, and the subsequent successful implementation in mass production since 2012, this development is also an excellent lesson of the challenges that must be overcome in the development of efficient industrial PV technology. Fraunhofer ISE has advanced this path over the past decades and has provided important technological and scientific impulses. This paper gives an overview about milestones in the more than 30 years lasting research activities on PERC at Fraunhofer ISE. With a conversion efficiency progress of +0.4%abs per year achieved for PERC devices since 2007, Fraunhofer ISE’s PV-TEC pilot-line is close to the progress reported from industrial pilot lines. We present insights into our latest process optimizations for PERC devices. Our champion power conversion efficiency of 23.4% is achieved on monofacial M2-format gallium-doped Cz-Si PERC solar cells with homogeneous emitter and front silver contacts featuring core finger widths of only 14 µm.