Phase Transitions and Dynamics in Mixed Three- and Low-Dimensional Lead Halide Perovskites

Abstract

Lead halide perovskites are extensively investigated as efficient solutionprocessable materials for photovoltaic applications. The greatest stability and performance of these compounds are achieved by mixing different ions at all three sites of the APbX 3 structure. Despite the extensive use of mixed lead halide perovskites in photovoltaic devices, a detailed and systematic understanding of the mixing-induced effects on the structural and dynamic aspects of these materials is still lacking. The goal of this review is to summarize the current state of knowledge on mixing effects on the structural phase transitions, crystal symmetry, cation and lattice dynamics, and phase diagrams of three-and low-dimensional lead halide perovskites. This review analyzes different mixing recipes and ingredients providing a comprehensive picture of mixing effects and their relation to the attractive properties of these materials.

Low-Temperature Persistent Disorder and Lattice Dynamics in a Luminescent 1D Hybrid Lead Halide: Implications and Insights

“…This behavior is interpreted as a dielectric signature of a phase transition between the LT and HT phases in AGAPbI 3 , as these temperature conditions closely align with the phase transition temperature determined from our calorimetric measurements upon heating (400 K). Moreover, a sudden increase of ε′ has been reported for many hybrid perovskites when crystal structures changed from ordered architectures with frozen molecular motions to disordered ones with rotated organic cations. − Dielectric behavior of AGAPbI 3 is therefore consistent with unlocking of AGA + rotations in the HT phase. The second dielectric anomaly is evident solely in the dielectric permittivity spectra of the LT phase for probe frequencies ranging from 1 × 10 0 to 1 × 10 6 Hz.…”

Temperature- and Pressure-Dependent Raman and Photoluminescence Studies of Corrugated Imidazolium-Methylhydrazinium Lead Bromide

“…Hybrid organic–inorganic lead halides have attracted enormous interest in recent years. One of the most studied subgroup are three-dimensional (3D) perovskites of APbX 3 stoichiometry, where A denotes a small organic cation (methylammonium, MA; formamidinium, FA; methylhydrazinium, MHy; aziridinium, AZR) and B stands for halogen (Cl, Br, I). − These compounds exhibit wide range of functional properties, including photovoltaic, photoluminescence (PL), and excellent multiphoton absorption. − They are, therefore, placed as strong candidates for new generation solar cells, light-emitting diodes (LEDs), and photodetectors . MHy-based analogues are exceptional in this category since they crystallize in the polar crystal structures and manifest the Second-Harmonic Generation (SHG), benefiting from the lack of the inversion center. − An important feature of MHy + is also its high dielectric permittivity and dipole moment. , It was demonstrated that these properties make MHyPbCl 3 attractive optical switch while MHyPbBr 3 exhibits switchable dielectric properties. , …”

Phonon Properties and Lattice Dynamics of Two- and Tri-Layered Lead Iodide Perovskites Comprising Butylammonium and Methylammonium Cations—Temperature-Dependent Raman Studies

“…Unfortunately, the 3D perovskites are rare and can be formed for a few small organic cations only, such as methylammonium (MA + ), formamidinium (FA + ), aziridinium (AZR + ), and methylhydrazinium (MHy + ) [ 3 , 4 , 5 , 6 , 7 , 8 , 9 ]. One of the methods to enhance the diversity and modify the properties of these 3D lead halide perovskites is the preparation of mixed systems [ 10 , 11 ]. A more efficient way is, however, the employment of larger organic cations, which allow the synthesis of various lower-dimensional structures [ 12 , 13 , 14 ].…”

“…To overcome problems with the large exciton binding energy of single-layered 2D perovskites, quasi-layered perovskites comprising two different cations can be synthesized. Most famous are Dion–Jacobson (DJ) (A′A n−1 Pb n X 3n+1 ) and Ruddlesden–Popper (RP) (A″ 2 A n−1 Pb n X 3n+1 ) compounds (n indicates the number of octahedral layers within each inorganic slab), in which small cage cations A are located in the voids of inorganic slabs and large divalent (A′) or monovalent (A″) cations separate the slabs [ 11 , 18 , 21 ]. It is worth adding that in such systems, an increase in the inorganic slab thickness (number of layers, n) improves photovoltaic properties [ 21 , 22 ].…”

“…This strength depends on the energy of phonon modes, the deformation of inorganic slabs, and the dynamics of organic cations [ 23 , 24 , 25 ]. The presence of organic components and the freezing of their dynamic molecular motions also afford an effective way for the generation of polar (ferro- or antiferroelectric) order [ 11 , 15 , 20 , 26 , 27 ]. It is therefore important to understand the effect of temperature on phonon properties, the dynamics of organic cations, and structural changes in hybrid perovskites.…”