To passivate defects in perovskite and enhance perovskite flims quality，a novel small molecule，2-amidinoethylenediamine dihydrobromide （2AD）， was designed for interfacial modification of mixed-cation mixed-halide perovskite （（FA_0.90MA_0.05Cs_0.05） Pb（I_0.96Br_0.04）₃） flims with a bandgap of 1.55 eV. The inverted perovskite solar cells （PSCs） were fabricated via an anti-solvent method using chlorobenzene， followed by systematic analysis of phase composition， optoelectronic properties， and device performance. Experimental results demonstrate the multifunctional effectiveness of 2AD in three key aspects： 1） the grain size of perovskite films increases from 304 nm to 321 nm， accompanied by reduces surface roughness from 16.6 nm to 15.8 nm， and enhances hydrophobicity contact angle from 70.1° to 74.3°，the hydrophobicity increases； 2） the photogenerated carrier lifetime is significantly prolonged， effectively suppressing non-radiative recombination and facilitating charge transfer； 3） unencapsulated devices retains over 90% of their initial power conversion efficiency after 30 d exposure to ambient atmosphere. Finally， the efficiency of the perovskite device increases from 21.32% to 23.49%， and the hysteresis factor significantly reduces.