Volker Sittinger, Tino Harig, Tobias Graumann, Sven Pleger, Christian Beyen, Fraunhofer Institute for Surface Engineering and Thin Film IST, Braunschweig, Germany
For future large-scale production of the electron contact layers in perovskite silicon tandem (PST) cells, optimized deposition systems and processes are required and must be adapted to each other. As a vacuum-based solution for electron contact, the established C₆₀/SnO₂ system is initially suitable for upscaling. To avoid negative ion bombardment of the C₆₀ and the underlying absorber, the electron contact C₆₀ is deposited by evaporation and the SnO₂ is deposited by atomic layer deposition. A new type of high-rate SALD hybrid system is used to develop the electron contact system. This system can be used to produce tunnel layers based on metal oxides on the perovskite absorber, as well as the subsequent electron contact layer using a linear evaporator technology developed in-house and the subsequent passivation layer. This work demonstrates the development of the SALD process for the Al₂O₃ tunnel layer and the SnO₂ barrier layer at low temperatures, as well as the combined approach of simulation, design, and implementation of the C₆₀ evaporator into the SALD system, along with the successive deposition of all layers on areas up to 250 mm wide, which allows for the deposition of G12 wafer sizes.