Perovskite-Like Organic–Inorganic Hybrid Lead Iodide with a Large Organic Cation Incorporated within the Layers

A great effort has
been made to investigate 2D perovskites to improve the stability and
controllability in the fabrication of photoelectronic devices. As
far as we know, only small organic cations such as methylammonium
can incorporate into the multilayered perovskite structure except
the cations sandwiched between the inorganic layers. We report here
a new layered lead iodide, (H2Aepz)3Pb4I14 (1), where larger organic cations, bis-protonated
2-(2-aminoethyl)­pyrazole (Aepz), not only were sandwiched between
the inorganic layers but also were incorporated within the perovskite-like
PbI layered structure. Another 2D compound, (H2Aepz)­PbI4 (2), was also prepared that was a one-layer
perovskite. A simple Schottky device was prepared to investigate the
photoelectroresponsive properties of the compounds in comparison with
that of a typical organic–inorganic hybrid perovskite. In general,
the energy gap is decreased with an increase in the perovskite layers,
but the band gap of two-layered 1 is larger than that
of one-layered 2. The photocurrent densities of the compounds
are in the order of 1 < 2 < (CH3NH3)­PbI3, which is discussed based on
the crystal structures and band energy gaps.