Thermo‐Mechanically Robust Inverted Perovskite Solar Cells Toward Extreme Environments

The long‐term reliability of inverted perovskite solar cells (PSCs) is compromised by instability at the buried hole‐transport‐layer (HTL) interface. State‐of‐the‐art HTLs face interfacial failure under thermal stress, owing to the labile chemical interactions of self‐assembled monolayers (SAMs) and the wetting‐limited physical contact of conventional polymers. Here, we develop PTPP, a phosphonic‐acid‐functionalized polymer that synergizes film continuity with robust SAM‐like anchoring, creating a cohesive interlayer for distributed dual‐sided engagement at the buried interface. We confirm that PTPP substantially enhances mechanical adhesion (3 fold) and suppresses thermally induced delamination by establishing a quantitative link between chemical interactions (binding energy) and macroscopic mechanics (fracture energy), while improving the crystallization homogeneity of the absorber. The devices based on the PTPP HTL achieve a PCE of 27.1% (certified 26.4%), retain 94.4% of their initial performance after 800 thermal cycles, and maintain 94.7% during 2000 h of continuous maximum power point (MPP) operation at 65°C under 1‐sun illumination. This chemo‐mechanical reinforcement ensures exceptional thermal‐cycling stability, enabling robust perovskite photovoltaics toward extreme environments.