Construction of 3D and 2D perovskites with N-methylpropane-1,3-diammonium as the organic cation and superior interlayer charge transport in the 3D perovskite single crystal photodetector

Abstract

A new type of three-dimensional structured AM₂X₆ (A = diammonium cation) combines the isotropic carrier transport of 3D organic–inorganic hybrid perovskites (OIHPs) and the stability of 2D OIHPs, holding promise for achieving a balance between efficiency and stability. However, current research on perovskites with this structure remains scarce, and the mechanism underlying the optoelectronic properties derived from their unique structure is still unclear. Herein, we synthesized 2D (NMPDA)PbBr₄ and 3D (NMPDA)Pb₂Br₆ (NMPDA = N-methylpropane-1,3-diammonium) single crystals, both of which use NMPDA as the organic cation. Density functional theory (DFT) calculations demonstrate that in comparison with 2D (NMPDA)PbBr₄, 3D (NMPDA)Pb₂Br₆ exhibits a larger carrier effective mass along the intralayer direction, while its carrier effective mass along the interlayer direction is significantly reduced. Meanwhile, (NMPDA)Pb₂Br₆ exhibits broadband luminescence, which may be associated with its significant distortion of individual octahedra and the fluctuation in Pb–Br bond strength caused by the uneven distribution of hydrogen bonds. Planar photodetectors based on (NMPDA)Pb₂Br₆ single crystals were fabricated. The responsivity and detectivity of the device exhibit significant anisotropy, with superior responsivity (8.47 mA W⁻¹) and detectivity (6.34 × 10¹¹ Jones) achieved along the interlayer direction. This study provides valuable theoretical insights into the structural design and optoelectronic properties of OIHPs.