Title | Key Aspects for Fabrication of p-Type Cz-Si PERC Solar Cells Exceeding 22% Conversion Efficiency |
Author(s) | Sabrina Lohmüller, Elmar Lohmüller, Pierre Saint-Cast, Johannes Greulich, Julian Weber, Stefan Schmidt, Anamaria Moldovan, Andreas Brand, Tobias Dannenberg, Sebastian Mack, Sven Wasmer, Matthias Demant, M. Linse, Rupprecht Ackermann, Andreas Wolf, Ralf Preu |
Keywords | Selective Emitter, Monocrystalline, p-Type, PERC, Solar Cells |
Topic | Silicon Photovoltaics |
Subtopic | Homojunction Solar Cells |
Event | EU PVSEC 2017 |
Session | 2CO.11.1 |
Pages manuscript | 406 - 412 |
ISBN | 3-936338-47-7 |
DOI | 10.4229/EUPVSEC20172017-2CO.11.1 |
This paper gives a close-up insight into recent and future developments that are performed with industrial focus at Fraunhofer ISE’s PV-TEC pilot-line to increase the energy conversion efficiency of 6-inch p-type Czochralski- grown silicon (Cz-Si) passivated emitter and rear cells (PERC) to 22% and above. First, the current status of PERC solar cell fabrication allowing for conversion efficiencies up to 21.5% is discussed. Then, we examine four key aspects in detail that need to be considered for optimizing the cells’ front side to boost the cell efficiency to the 22% regime. We demonstrate selective emitter laser doping out of the phosphosilicate glass layer, which is formed by a gas phase phosphorus oxychloride diffusion process. After diffusion and wet-chemical emitter etch back, the field emitter features a very low saturation current density of only 31 fA/cm² (textured, SiNx-passivated). Specific contact resistances of 1 mΩcm2 confirm the low-resistance contacting of the laser-doped surfaces using a commercially available silver screen printing paste. Apart from developing an accurate alignment procedure to match laserstructured and screen-printed layouts, we have also optimized our single-step screen-printing process for finger widths of 38 μm at 16 μm height. Based on simulations we find that efficiencies up to 22.5% are possible when the optimized process routes are integrated into PERC solar cells.