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.