Abstract: The development of wide-bandgap perovskite solar cells is limited by the high defect density and severe non-radiative recombination within their films. This study proposes the use of 4-methoxyphenyldiethylphosphonate （DM） as a multifunctional additive to mitigate these problems. The P＝O group in the DM molecule can form stable coordination bonds with under-coordinated Pb²⁺， effectively passivating defects. Simultaneously， its methoxy group regulates the local charge distribution through an electron-donating effect， thereby synergistically optimizing the crystallization process. Furthermore， the π-π stacking interactions between the benzene rings of DM molecules enhance the film's hydrophobicity， thereby improving environmental stability. The DM-modified wide-bandgap perovskite solar cell achieve a power conversion efficiency （PCE） of 22.08%. In contrast， the PCE of the control device without DM is only 18.89%. Furthermore， DM modification increase the open-circuit voltage （V_oc） from 1.082 V to 1.127 V， the short-circuit current density （J_sc） from 22.33 mA·cm^-2 to 23.78 mA·cm^-2， and the fill factor （FF） from 78.17% to 82.39%. The unencapsulated DM-modified device retained 91.2% of its initial efficiency after 30 d of storage at 25 ℃ and 10%~40% relative humidity， significantly outperforming the control device（85.3%）. These results strongly demonstrate the significant potential of DM as a functional additive for fabricating high-quality perovskite films and realizing high-performance devices， laying both experimental and theoretical foundations for its subsequent practical application.

Key words: wide-bandgap perovskite solar cell; defect passivation; non-radiative recombination; additive engineering; crystallization modulation; stability