Water assisted high proton conductance in a pure-inorganic framework vanadoborate

A new pure-inorganic framework vanadoborate H10[V12B18O54(OH)6]•20H2O (1) was hydrothermally synthesized and structurally characterized. Its inorganic framework was constructed by discrete [V12B18O54(OH)6]10- polyanion clusters decorated with H+ as counterions. For 1,...

High-throughput computational material screening of the cycloalkane-based two-dimensional Dion–Jacobson halide perovskites for optoelectronics

Two-dimensional (2D) layered perovskites have emerged as potential alternates to traditional 3D analogs to solve the stability issue of perovskite solar cells. In recent years, many efforts have been spent on manipulating the interlayer organic spacing cation to improve the photovoltaic properties of Dion–Jacobson (DJ) perovskites. In this work, a serious of cycloalkane (CA) molecules were selected as the organic spacing cation in 2D DJ perovskites, which can widely manipulate the optoelectronic properties of DJ perovskites. The underlying relationship between the CA interlayer molecules and the crystal structures, thermodynamic stabilities, and electronic properties of 58 DJ perovskites has been investigated by using automatic high-throughput workflow cooperated with density-functional (DFT) calculations. We have found that these CA-based DJ perovskites are all thermodynamic stable. The sizes of the cycloalkane molecules can influence the degree of inorganic framework distortion and further tune the bandgaps with a wide range of 0.9~2.1 eV. These findings indicate the cycloalkane molecules are suitable for spacing cation in 2D DJ perovskites and provide a useful guidance in designing novel 2D DJ perovskites for optoelectronic applications.

Ultrafast femtosecond pressure modulation of structure and exciton kinetics in 2D halide perovskites for enhanced light response and stability

The carriers’ transportation between layers of two-dimensional (2D) perovskites is inhibited by dielectric confinement. Here, for the first time, we employ a femtosecond laser to introduce ultrafast shock pressure in the range of 0~15.45 GPa to reduce dielectric confinement by modulating the structure and exciton dynamics in a perovskite single crystal (PSCs), e.g. (F-PEA)2PbI4 (4-fluorophenethylammonium, F-PEA). The density functional theory (DFT) simulation and experimental results show that the inorganic framework distortion results in a bandgap reduction. It was found that the exciton-optical phonon coupling and free excitons (FEs) binding energy are minimized at 2.75 GPa shock pressure due to a reduction in dielectric confinement. The stability testing under various harsh light and humid thermal conditions shows that femtosecond laser shocking improves the stability of (F-PEA)2PbI4 PSCs. Femtosecond laser shock processing provides a new approach for regulating the structure and enhancing halide perovskite properties.

Order–disorder transition of a rigid cage cation embedded in a cubic perovskite

The structure and properties of organic–inorganic hybrid perovskites are impacted by the order–disorder transition, whose driving forces from the organic cation and the inorganic framework cannot easily be disentangled. Herein, we report the design, synthesis and properties of a cage-in-framework perovskite AthMn(N3)3, where Ath+ is an organic cation 4-azatricyclo[2.2.1.02,6]heptanium. Ath+ features a rigid and spheroidal profile, such that its molecular reorientation does not alter the cubic lattice symmetry of the Mn(N3)3− host framework. This order–disorder transition is well characterized by NMR, crystallography, and calorimetry, and associated with the realignment of Ath+ dipole from antiferroelectric to paraelectric. As a result, an abrupt rise in the dielectric constant was observed during the transition. Our work introduces a family of perovskite structures and provides direct insights to the order–disorder transition of hybrid materials.

Room-Temperature Phosphorescent Organic-Doped Inorganic Frameworks Showing Wide-Range and Multicolor Long-Persistent Luminescence

Long-persistent luminescence based on purely inorganic and/or organic compounds has recently attracted much attention in a wide variety of fields including illumination, biological imaging, and information safety. However, simultaneously tuning the static and dynamic afterglow performance still presents a challenge. In this work, we put forward a new route of organic-doped inorganic framework to achieve wide-range and multicolor ultralong room-temperature phosphorescence (RTP). Through a facile hydrothermal method, phosphor (tetrafluoroterephthalic acid (TFTPA)) into the CdCO3 (or Zn2(OH)2CO3) host matrix exhibits an excitation-dependent colorful RTP due to the formation of diverse molecular aggregations with multicentral luminescence. The RTP lifetime of the doped organic/inorganic hybrids is greatly enhanced (313 times) compared to the pristine TFTPA. The high RTP quantum yield (43.9%) and good stability guarantee their easy visualization in both ambient and extreme conditions (such as acidic/basic solutions and an oxygen environment). Further codoped inorganic ions (Mn2+ and Pb2+) afford the hybrid materials with a novel time-resolved tunable afterglow emission, and the excitation-dependent RTP color is highly adjustable from dark blue to red, covering nearly the whole visible spectrum and outperforming the current state-of-the-art RTP materials. Therefore, this work not only describes a combined codoping and multicentral strategy to obtain statically and dynamically tunable long-persistent luminescence but also provides great opportunity for the use of organic-inorganic hybrid materials in multilevel anticounterfeiting and multicolor display applications.

Reconfiguring the band-edge states of photovoltaic perovskites by conjugated organic cations

The band edges of metal-halide perovskites with a general chemical structure of ABX3 (A, usually a monovalent organic cation; B, a divalent cation; and X, a halide anion) are constructed mainly of the orbitals from B and X sites. Hence, the structural and compositional varieties of the inorganic B–X framework are primarily responsible for regulating their electronic properties, whereas A-site cations are thought to only help stabilize the lattice and not to directly contribute to near-edge states. We report a π-conjugation–induced extension of electronic states of A-site cations that affects perovskite frontier orbitals. The π-conjugated pyrene-containing A-site cations electronically contribute to the surface band edges and influence the carrier dynamics, with a properly tailored intercalation distance between layers of the inorganic framework. The ethylammonium pyrene increased hole mobilities, improved power conversion efficiencies relative to that of a reference perovskite, and enhanced device stability.

Order–Disorder Transition of a Rigid Cage Cation Embedded in a Cubic Perovskite

The structure and properties of organic–inorganic hybrid perovskites are impacted by the order–disorder transition, whose driving forces from the organic cation and the inorganic framework cannot easily be disentangled. Herein, we report the design, synthesis and properties of a cage-in-framework perovskite AthMn(N3)3, where Ath+ is an organic cation 4-azatricyclo[2.2.1.02,6]heptanium. Ath+ features a rigid and spheroidal profile, such that its molecular reorientation does not alter the cubic lattice symmetry of the Mn(N3)3− host framework. This pure order–disorder transition is well characterized by NMR, crystallography, and calorimetry, and associated with the realignment of Ath+ dipole from antiferroelectric to paraelectric. As a result, an abrupt rise in the dielectric constant was observed during the transition. Our work introduces a new family of perovskite structures and provides direct insights to the order–disorder transition of hybrid materials.