From 2D to 1D Electronic Dimensionality in Halide Perovskites with Stepped and Flat Layers Using Propylammonium as a Spacer

Two-dimensional (2D) hybrid halide perovskites are promising in optoelectronic applications, particularly solar cells and light emitting devices (LEDs), and for their increased stability compared to 3D perovskites. Here, we report a new series of structures using propylammonium (PA+) which results in a series of Ruddlesden-Popper (RP) structures with the formula (PA)2(MA)n-1PbnI3n+1 (n = 3, 4) and a new homologous series of “step-like” (SL) structures where the PbI6 octahedra connect in a corner- and face-sharing motif with the general formula (PA)2m+4(MA)m-2Pb2m+1I7m+4 (m = 2, 3, 4). The RP structures show a blue-shift in bandgap for decreasing n (1.90 eV for n = 4 and 2.03 eV for n = 3) while the SL structures have an even greater blue-shift (2.53 eV for m = 4, 2.74 eV for m = 3, and 2.93 eV for m = 2). DFT calculations show that, while the RP structures are electronically 2D quantum wells, the SL structures are electronically 1D quantum wires with chains of corner-sharing octahedra “insulated” by block...