Perovskite Films with High Phase Purity in Mesopores for Efficient Carbon‐based Mesoscopic Perovskite Solar Cells

ABSTRACT The phase purity of perovskite films within mesoporous scaffolds is crucial for the performance of carbon‐based mesoscopic perovskite solar cells (MPSCs). A competitive coordination strategy using an acetamide‐nicotinamide binary eutectic molecule (EM) is proposed to enhance the phase purity and the performance of the MPSCs. The EMs form an ordered assembly via strong N─H···O═C hydrogen bonds, which ensures uniform dispersion, synergistic coordination, and retained defect passivation, while the hydrogen‐bond network disperses charge density at coordination sites. Furthermore, the EMs prevent excessive Pb 2+ binding and promote ordered growth of [PbI 6 ] 4− along the direction of the mesoporous. The optimized MPSCs with EM achieve a power conversion efficiency of 21.30%, increased from 18.83% of the control devices. And the unencapsulated MPSCs maintain ∼82% of their initial value after 900 h stored under ambient air.