Guanidinium-Formamidinium Lead Iodide: A Layered Perovskite-Related Compound with Red Luminescence at Room Temperature

Two-dimensional
hybrid organic–inorganic lead halides perovskite-type
compounds have attracted immense scientific interest due to their
remarkable optoelectronic properties and tailorable crystal structures.
In this work, we present a new layered hybrid lead halide, namely
[CH­(NH2)2]­[C­(NH2)3]­PbI4, wherein puckered lead-iodide layers are separated by two
small and stable organic cations: formamidinium, CH­(NH2)2+, and guanidinium, C­(NH2)3+. This perovskite is thermally stable up to 255
°C, exhibits room-temperature photoluminescence in the red region
with a quantum yield of 3.5%, and is photoconductive. This study highlights
a vast structural diversity that exists in the compositional space
typically used in perovskite photovoltaics.