Two-Dimensional Halide Pb-Perovskite–Double Perovskite Epitaxial Heterostructures

Abstract

Epitaxial heterostructures of two-dimensional (2D) halide perovskites offer a new platform for studying intriguing structural, optical, and electronic properties. However, difficulties with the stability of Pb- and Sn-based heterostructures have repeatedly slowed the progress. Recently, Pb-free halide double perovskites are gaining a lot of attention due to their superior stability and greater chemical diversity, but they have not been successfully incorporated into epitaxial heterostructures for further investigation. Here, we report epitaxial core-shell heterostructures via growing Pb-free double perovskites (involving combinations of Ag­(I)–Bi­(III), Ag–Sb, Ag–In, Na–Bi, Na–Sb, and Na–In) around Pb perovskite 2D crystals. Distinct from Pb–Pb and Pb–Sn perovskite heterostructures, growths of the Pb-free shell at 45° on the (100) surface of the lead perovskite core are observed in all Pb-free cases. The in-depth structural analysis carried out with electron diffraction unequivocally demonstrates the growth of the Pb-free shell along the [110] direction of the Pb perovskite, which is likely due to the relatively lower surface energy of the (110) surface. Furthermore, an investigation of anionic interdiffusion across heterostructure interfaces under the influence of heat was carried out. Interestingly, halide anion diffusion in the Pb-free 2D perovskites is found to be significantly suppressed as compared to Pb-based 2D perovskites. The great structural tunability and excellent stability of Pb-free perovskite heterostructures may find uses in electronic and optoelectronic devices in the near future.

Two-Dimensional Double Perovskites in the Dion–Jacobson Phase Alleviate Parity Forbidden Transitions for Photovoltaic Applications

“…DPKs have been established to display parity-forbidden transitions in a number of materials which would otherwise serve as highly desirable photovoltaics. − 2DPKs, on the other hand, struggle with wider bandgaps when compared with their bulk counterparts, particularly when the layer thickness, n , is on the order of 1–5 . Combinations of double perovskites and two-dimensional perovskites, herein referred to as 2DDPKs, have only emerged very recently in the literature. − The introduction of 2DDPKs allows for many combinations of monovalent and trivalent cations to mitigate the wide bandgap concerns of 2DPKs, as well as selection of the A′ spacing cations to reduce symmetry and alleviate the otherwise forbidden optical transitions at the band edge. While the potential of 2DDPKs is very promising, limited research has been carried out on a subset of these materials simultaneously to aid in generalizing the key structure–property relationships in this subclass of perovskites .…”

On-Wire Design of Axial Periodic Halide Perovskite Superlattices for High-Performance Photodetection

“…All-inorganic lead halide perovskite nanowires are considered to be a candidate material for integrated photonics owing to their unique chemical and physical properties. − The development of perfect ways to engineer lead halide perovskite structures with controllable bandgaps and optoelectronic properties is an active research topic in materials science and technology, which may lead to promising applications in the future. − Especially, bandgap engineering along single-perovskite complex structures could provide an effective way for constructing highly integrated, − low power consumption, and miniaturized optoelectronic devices, including all-optical switches, , light-emitting diodes, , optical logic gates, lasers, , solar cells, , and photodetectors. − …”