Mechanical Reliability of Fullerene/Tin Oxide Interfaces in Monolithic Perovskite/Silicon Tandem Cells

High-efficiency perovskite-based solar cells comprise sophisticated stacks of materials which, however, often feature different thermal expansion coefficients and are only weakly bonded at their interfaces. This may raise concerns over delamination in such devices, jeopardizing their long-term stability and commercial viability. Here, we investigate the root causes of catastrophic top-contact delamination we observed in state-of-the-art p-i-n perovskite/silicon tandem solar cells. By combining macroscopic and microscopic analyses, we identify the interface between the fullerene electron transport layer and the tin oxide buffer layer at the origin of such delamination. Specifically, we find that the perovskite morphology and its roughness play a significant role in the microscopic adhesion of the top layers, as well as the film processing conditions, particularly the deposition temperature and the sputtering power. Our findings mandate the search for new interfacial linking strategies to enable mechanically strong perovskite-based solar cells, as required for commercialization.

Automated summary

This study investigates the root causes of catastrophic delamination at the top contact in state-of-the-art perovskite/silicon tandem solar cells and identifies the interface between the fullerene electron transport layer and the tin oxide buffer layer as the origin of such delamination. The study shows that the perovskite morphology and roughness, as well as the film processing conditions, play significant roles in the microscopic adhesion of the top layers. These findings highlight the need for new interfacial linking strategies to enable mechanically strong perovskite-based solar cells for commercialization.