Inkjet- and flextrail-printing of silicon polymer-based inks for local passivating contacts

In this work innovative additive printing methods for formation of polycrystalline silicon (poly-Si) and polycrystalline silicon carbide (poly-SiC) layers of local tunnel oxide passivating contacts (TOPCon) is evaluated. Replacement of conventional vacuum processes and vapor-phase deposition by additive printing of Si in fabrication process of high efficiency solar cells reduces processing complexity, and, hence manufacturing costs. Reliable inkjet- and FlexTrail-printing processes are developed for liquid-phase polysilane and organic polysilazane inks that are precursors of Si and SiC, respectively. FlexTrail is introduced as a potential technology to print uniform closed thin films of polysilane free of ruptures. Moreover, from inkjet-printing of the developed polysilane ink, homogenous, closed and crack free thin films of poly-Si are obtained after high temperature annealing. The polysilane ink is formulated considering evaluation of several solvents and photoinduced polymerization conditions. Inkjet-printing process development and optimization according to high frequency rheological characterization of organic polysilazane (OPSZ) is presented. Printed thin films are characterized after high temperature annealing (T = 950 °C, t = 60 min) to be uniform and free of micro cracks.