Multidentate anchoring strategy for synergistically modulating crystallization and stability towards efficient perovskite solar cells

CsFAMA-based perovskite solar cells (PSCs) have become promising photovoltaic materials due to their excellent photovoltaic properties. However, the inherent instability of perovskite severely hinders its commercialization, since the typical ionic nature of perovskite can cause the ionic migration and volatilization of organic components. Herein, allantoin molecules with multiple alternating carbonyl (C = O) and amino (-NH2 or -NH-) groups were introduced as a multidentate additive to synergistically anchor the perovskite components and passivate the defects, resulting in non-radiative recombination and ion migration being not susceptible to occur. Due to the favorable attraction ability of allantoin to the perovskite precursor monomers and the formation of hydrogen bonds between FAI/MAI and allantoin, the crystal quality of perovskite was significantly improved and the bulk/ interface defects were effectively eliminated. Specifically, the interaction between allantoin and FA+/MA+ can suppress their deprotonations and prevent the volatilization of organic cations from the initial precursor solutions, drastically reducing the wastage of precursor materials. Consequently, the modified devices demonstrated a prominent elevation of performance with a higher efficiency of 21.49 %, which was better than that of control (19.67 %). Moreover, the modified perovskite films also demonstrated prominent stability under the continuous illumination and moisture aging owing to the reduction of trap defects. The allantoin additives also greatly enhanced the hydrophobicity of perovskite, and the modified device maintained 90 % of its initial efficiency for 1680 h at 10-20 % relative humidity without encapsulation.