The Rb 7 Bi 3−3 x Sb 3 x Cl 16 Family: A Fully Inorganic Solid Solution with Room‐Temperature Luminescent Members

Polymorphism and Red Photoluminescence Emission from 5s2 Electron Pairs of Sb(III) in a New One-Dimensional Organic-Inorganic Hybrid Based on Methylhydrazine: MHy2SbI5

We explore the crystal structure and luminescent properties of a new 1D organic-inorganic hybrid, MHy2SbI5, based on methylhydrazine. The compound reveals the red photoluminescence (PL) originating from the 5s2 electron pairs of Sb(III) as well as complex structural behavior. MHy2SbI5 crystalizes in two polymorphic forms (I and II) with distinct thermal properties and structural characteristics. Polymorph I adopts the acentric P212121 chiral space group confirmed by SHG, and, despite a thermally activated disorder of MHy, does not show any phase transitions, while polymorph II undergoes reversible low-temperature phase transition and high-temperature reconstructive transformation to polymorph I. The crystal structures of both forms consist of 1D perovskite zig-zag chains of corner-sharing SbI6 octahedra. The intriguing phase transition behavior of II is associated with the unstable arrangement of the [SbI5]2-∞ chains in the structure. The energy band gap (Eg) values, estimated based on the UV-Vis absorption spectra, indicate that both polymorphs have band gaps, with Eg values of 2.01 eV for polymorph I and 2.12 eV for polymorph II.

Sb3+-Er3+-Codoped Cs2NaInCl6 for Emitting Blue and Short-Wave Infrared Radiation

Cs 2 NaInCl 6 double perovskite is stable, environmentally benign, and can be prepared easily. But it has high band gap (5.1 eV), and therefore, does not show optical and optoelectronic properties in the visible and short-wave infrared (SWIR) region. Here we introduce such functionalities in Cs 2 NaInCl 6 by codoping Sb 3+ ( s -electron doping) and Er 3+ ( f -electron doping). Sb 3+ doping introduces optically allowed 5 s 2 → 5 s 1 5 p 1 electronic absorption at the sub band gap level, which then emit blue light with ~93% photoluminescence quantum yield. On the other hand, f-f electronic absorption of Er 3+ is parity forbidden. Codoping Sb 3+ -Er 3+ , leads to transfer of excitation energy from Sb 3+ to Er 3+ , yielding SWIR emission at 1540 nm that falls in the optical fiber communication region. Temperature (6 to 300 K) dependent photoluminescence measurements elucidate the excitation mechanism in the codoped Cs 2 NaInCl 6 . Further, we have fabricated phosphor converted light emitting diode (pc-LED) by coating the codoped sample on commercial ultraviolet LED chips. The pc-LED emit stable blue and SWIR radiation over prolonged operation (over 84 hours) at 5.1 V.

Pressure Tuning of Optical Properties and Structures in All-Inorganic Halide Perovskite Rb7Sb3Cl16

All lead-free inorganic halide perovskites, as efficient solid-state light emission materials, have become ideal green optoelectronic materials to replace lead halide perovskites for diversified lighting and display applications with their excellent stability. Here, we investigated the pressure-derived optical and structural response of a zero-dimensional lead-free perovskite Rb₇Sb₃Cl₁₆ through applying controllable pressure. A pressure-induced blue shift of the broadband emission was achieved, and it was followed by the emission color transformation from yellow to green, which was ascribed to the electron-phonon coupling weakening and the suppression of structural deformation upon lattice contraction. In parallel, the band gap was narrowed by about 0.5 eV as a result of enhanced metal halide orbital overlap under high pressure. This work provides a fundamental understanding for modulating the optical properties of the low-dimensional metal halide perovskites.

Modulation of the optical bandgap and photoluminescence quantum yield in pnictogen (Sb3+/Bi3+)-doped organic-inorganic tin(IV) perovskite single crystals and nanocrystals

Water-stable, lead-free zero-dimensional (0D) organic-inorganic hybrid colloidal tin(IV) perovskite, A₂SnX₆ (A is a monocationic organic ion and X is a halide) nanocrystals (NCs) with high photoluminescence (PL) quantum yield (QY) have rarely been explored. Herein, we report solution-processed colloidal NCs of blue light-emitting T₂SnCl₆ and orange light-emitting T₂Sn_1-xSb_xCl₆ [T⁺ = tetramethylammonium cation] from their corresponding single crystals (SCs). These colloidal NCs are well-dispersible in non-polar solvents, thereby maintaining their bright emission. This paves the way for fabricating homogeneous thin films of these NCs. Due to organic cation (T⁺)-controlled large spin-orbit coupling (SOC), the T₂Sn_1-xSb_xCl₆ NCs exhibit bright orange emission with an enhancement in PL QY of 41% compared to their bulk counterpart. Furthermore, we explore T₂Sn_1-xBi_xCl₆ and T₂Sn_1-x-yBi_xSb_yCl₆ SCs, which show blue and green emission, respectively; the latter is attributed to the newly formed Sb 5p and Sb 5 s orbital-driven band structures confirmed by applying density functional theory (DFT) calculations. The SCs and NCs exhibit excellent stability in water under ambient conditions because of the in-situ generation of a hydrophobic and oxygen-resistant passivating layer of oxychloride in the presence of water. Our findings open a pathway for designing lead-free perovskites materials for thin-film-based optoelectronic devices.

Recent Advances in All-Inorganic Zero-Dimensional Metal Halides

All-inorganic zero-dimensional (0D) metal halides are composed of isolated metal halide polyhedrons bridged by monovalent alkali metal ions. The unique structure gives rise to molecule-like electronic configuration and consequently highly attractive optical properties. In comparison with their three-dimensional (3D) counterparts, the 0D metal halides exhibit characteristic features such as broadband emission and long-term stability. In addition, 0D metal halides can be constructed from a diverse range of metal ions and permit high-level impurity doping, thereby offering great structural designability and spectral tunability. This Review surveys recent advances in 0D metal halides, including crystal preparation, luminescence modulation, and emerging applications.