Non-Volatile Multifunctional Dipole Molecules Enable 19.2% Efficiency for Printable Mesoscopic Perovskite Solar Cells

Dipole molecules (DMs) show great potential in defect passivation for printable mesoscopic perovskite solar cells (p-MPSCs), although the crystallization process of p-MPSCs is more intricate and challenging than planar perovskite solar cells. In this work, a series of non-volatile multifunctional DMs are employed as additives to enhance the crystallization of perovskites and improve both the power conversion efficiency (PCE) and stability of the devices. This enhancement is achieved by regulating the side groups of benzoic acid molecules with the electron-donating groups such as guanidine (─NH─C(═NH)─NH₂), amino (─NH₂) and formamidine (─C(═NH)─NH₂). DMs form hydrogen bond interactions with the organic cations of perovskite and establish electrostatic interactions with PbI₆ ^4-. The synergistic effect of these interactions suppresses PbI₂ formation, enhances perovskite film crystalline quality, reduces perovskite crystal defect density, mitigates non-radiative recombination, and effectively enhances carrier transfer and extraction efficiency. Furthermore, the incorporation of DMs leads to a reconstruction of the perovskite film surface energy level, thereby enhancing hole extraction efficiency at the perovskite/carbon electrode interface. The optimized p-MPSCs achieve a PCE of 19.23%. The unencapsulated device demonstrates promising long-term storage stability, retaining 91% of the original PCE after 1440 h of aging at 40 ± 5% relative humidity and 30 ± 5 °C.