Front SiON/TCO Stacks Development for Double Side Poly-Si/SiOX Passivated Contacts Solar Cells

This work reports on the use of a front side SiON/TCO bilayer in double side poly-Si/SiOX-based passivated contacts solar cells. This approach presents the advantage of a low indium consumption either by reducing the indium-based transparent conductive oxide (TCO) thickness or by enhancing its substitution with a Zinc-based TCO, such as AZO (Aluminum-doped Zinc Oxide). An electrical study with a TCO thickness reduced to 20 nm on textured surfaces has shown excellent responses for SiON/AZO stacks, especially regarding the contact resistivity. The developed SiON/TCO bilayers were finally integrated in complete solar cells. Interestingly, the substitution of the standard 70 nm-thick ITO:H layer by a 20 nm-thick ITO:H film covered by SiON led to an efficiency gain of +0.5% abs. Regarding AZO, the replacement of the standard 70 nm-thick AZO layer by a 20 nm-thick AZO film covered by SiON conducted to a JSC gain of +0.8 mA/cm2. These gains in performances could be raised with further post-treatments still under investigation. However, the current results already confirm the possibility to optimize thin-poly-Si based passivated contacts solar cells towards In-free fabrication processes.