Elucidating the Impact of Buried Interface Engineering on Perovskite Properties and Stability in Inverted Perovskite Solar Cells.

Buried-interface engineering is crucial in the fabrication of perovskite solar cells (PSCs) due to its effectiveness in facilitating the deposition of perovskite absorbers. This technique is especially significant in inverted PSCs (IPSCs) where the dewetting materials are normally used as the bottom hole transporters. Here, we investigate the impact of buried-interface techniques on the optical and mechanical behavior of perovskites and the overall stability of IPSCs. Our findings demonstrate that the chemical treatment with fluorene-based conjugated polyelectrolyte (e.g., PFN-Br), in contrast to the physical UV-ozone method, induces distinct dendrite-like patterns at the buried interface. These changes profoundly impact the optical properties of the perovskite films, evidenced by red-shifted photoluminescence in these regions. Furthermore, the dendritic morphologies are shown to affect the mechanical properties of the as-crystallized perovskite films, such as a reduction in Young's modulus/hardness, which in turn modulate the device performance. The photovoltaic data indicate that these dendrite-like patterns are beneficial for the initial efficiencies but compromise the long-term stability of the derived IPSCs. This study provides valuable insights into buried-interface engineering strategies for achieving efficient and stable IPSCs.