Molecular press annealing enables robust perovskite solar cells

Thermal annealing improves the crystallinity of perovskite films and boosts their power conversion efficiencies (PCEs) in solar cells but also induces surface iodine loss and local lattice degradation. We demonstrate a molecular press annealing (MPA) strategy in which a 2-pyridylethylamine film is thermally and pressure-bonded to the perovskite surface. Real-time healing of iodine vacancies occurred during annealing and the lead-iodine framework was stabilized through optimized ligand engineering, resulting in enhanced structural integrity and long-term stability of perovskite films. This strategy enabled n-i-p perovskite solar cells to achieve a PCE of 26.6% (certified 26.5%). Notably, the devices retain 98.6 and 97.2% of their initial PCEs after 1617 hours of continuous operation under maximum power point tracking [ISOS-L-3 protocol, 85°C, 60% relative humidity (RH)] and 5280 hours of ambient storage (ISOS-D-1 protocol, room temperature, 10% RH).