Halide Ordering Enables Superior Charge Transport in 3D (NMPDA)Pb₂ I₄ Br₂ Perovskitoid Single Crystal

Halide composition engineering has been demonstrated as an effective strategy for optical and electronic properties modulation in 3D perovskites. While the impact of halide mixing on the structural and charge transport properties of 3D perovskitoids remains largely unexplored. Herein, it is demonstrated that bromine (Br) mixing in 3D (NMPDA)Pb₂ I₆ (NMPDA = N-methyl-1,3-propane diammonium) perovskitoid yields stabilized (NMPDA)Pb₂ I₄ Br₂ with specific ordered halide sites, where Br ions locate at the edge-sharing sites. The halide ordered structure enables stronger H-bonds, shorter interlayer distance, and lower octahedra distortion in (NMPDA)Pb₂ I₄ Br₂ with respect to the pristine (NMPDA)Pb₂ I₆ . These attributes further result in high ion migration activation energy, low defect states density, and enhanced carrier mobility-lifetime product (µτ), as underpinned by the electrical properties investigation and DFT calculations. Remarkably, the parallel configured photodetector based on (NMPDA)Pb₂ I₄ Br₂ single crystal delivers a high on/off current ratio of 3.92 × 10³ , a satisfying photoresponsivity and detectivity of 0.28 A W^-1 and 3.05 × 10¹² Jones under 10.94 µW cm^-2 irradiation, superior to that of (NMPDA)Pb₂ I₆ and the reported 3D perovskitoids. This work sheds novel insight on exploring 3D mixed halide perovskitoids toward advanced and stable optoelectronic devices.