The extraordinary structural stability of Dion Jacobson (DJ) phase two-dimensional (2D) perovskites, which are created by integrating diammonium cation spacers into the organic-inorganic perovskite structure with a uniformly ordered configuration, has piqued the interest of scientists. In this study, a solution of diammonium cation spacer based on 1,4-Phenylenediammonium iodide (PDAI) in IPA is spin-coated on top of 3D triple cation (Cs_0.05(FA_0.83MA_0.17)_0.95Pb(I_0.83Br_0.17)₃) perovskite films toward a 2D-3D mixed-structure. The 2D topping layer based on DJ phase passivated surface imperfections, reduced charge recombination at contact surfaces, and boosted the optoelectronic characteristics of the formed 2D-3D perovskite materials, which are attributed to the hydrogen bonding interaction of NH₃⁺ and (PbI₆)^- octahedra. The PCE of the perovskite device has been remarkably enhanced from 19.77 to 21.15%, and the PDA-treated perovskite presented better stability studies than the untreated. Moreover, this improved environmental resistance and gradient energy levels at connection interfaces aided hole injection from the 3D perovskite to Spiro-OMeTAD, while inhibiting electrons from recombining with holes. It is essential to mention that the significant improvement in PCE came from Voc and FF. The improved device efficiency was attributed mainly to further effective inhibition of unwanted non-radiative recombination as well as the resulting decreased recombination centers.