Inexpensive and highly efficient luminescent materials based on multinary halides have received increased attention in recent years. Among those considered most promising are the perovskites such as CsPbX3 because of their highly efficient and tunable emission through precise control of chemical composition and nanostructuring. However, the presence of the toxic heavy metal Pb and relatively poor stability are among the major challenges for the introduction of lead-halide-based materials into the marketplace. Here, we report the optical properties of nontoxic and highly emissive one-dimensional (1D) all-inorganic halides CsCu2X3 (X = Cl, Br, I) and their mixed halide derivatives, which also show improved thermal and air stability. Photoluminescence (PL) measurements show tunable bright room temperature emission from green to yellow with photoluminescence quantum yields ranging from 0.37 (CsCu2Cl1.5Br1.5) to 48.0% (CsCu2Cl3). Temperature- and power-dependent PL measurements suggest that the emission results from self-trapped excitons induced by strong charge localization and structural distortions within the lD ribbon structure.

Low-dimensional hybrid organic–inorganic materials (HOIMs) are being widely investigated for their unique optoelectronic properties. Some of them exhibit broadband white-light (WL) luminescence upon UV excitation, providing a potential for the fabrication of single-component white-light-emitting diodes. Here, we report new examples of low-dimensional HOIMs, based on 4-aminopyridinium (4AMP) and group 12 metals (Hg and Zn), for single-component WL emission. The 4AMP cation containing structures feature HgBr4 and ZnBr4 isolated tetrahedra in (C5H7N2)2HgBr4·H2O (1) and (C5H7N2)2ZnBr4 (2), respectively. The presence of isolated molecular units in the zero-dimensional structures results in strongly localized charges and bright WL luminescence with corresponding Commission Internationale de l’Eclairage color coordinates of (0.34, 0.38) and (0.25, 0.26), correlated color temperatures of 5206 K (1) and 11 630 K (2), and very high color rendering indexes (CRI) of 87 (1) and 96 (2). The visibly bright WL emission at room temperature is corroborated with high measured photoluminescence quantum yield values of 14.87 and 19.18% for 1 and 2, respectively. Notably, the high CRI values for these new HOIMs exceed the commercial requirements and produce both “warm” and “cold” WL depending on the metal used (Hg or Zn). Based on temperature- and powder-dependent photoluminescence (PL), PL lifetimes measurements and density functional theory calculations, the broadband WL emission is assigned to the 4AMP organic molecules emission and self-trapped states.

Recently, interest in developing efficient, low-cost, nontoxic, and stable metal halide emitters that can be incorporated into solid-state lighting technologies has taken hold. Here we report nontoxic, stable, and highly efficient blue-light-emitting Cs3Cu2Br5–x I x (0 ≤ x ≤ 5). Room-temperature photoluminescence measurements show bright blue emission in the 456 to 443 nm range with near-unity quantum yield for Cs3Cu2I5. Density functional theory calculations and power-dependent PL measurements suggest that the emission results from self-trapped excitons induced by strong charge localization within the zero-dimensional cluster structure of Cs3Cu2Br5–x I x .

The United States Department of Energy (DOE) projects an estimated energy cost savings of $630 billion from 2015 to 2035 if reliable solid-state lighting technologies can be developed and DOE goals are met. [1] For the cost-effective implementation of light-emitting diodes (LEDs), development of new inexpensive light emitters is an urgent need. Owing to their outstanding photophysical properties including tunable bandgaps and emission colors, high photoluminescent quantum yields (PLQY) and excellent color purity, metal halide perovskite LEDs (PeLEDs)

We report the synthesis, crystal and electronic structures, as well as optical properties of the hybrid organic-inorganic compounds MACdX (MA = CHNH; X = Cl, Br, I). MACdI is a new compound, whereas, for MACdCl and MACdBr, structural investigations have already been conducted but electronic structures and optical properties are reported here for the first time. Single crystals were grown through slow evaporation of MACdX solutions with optimized conditions yielding mm-sized colorless (X = Cl, Br) and pale yellow (X = I) crystals. Single crystal and variable temperature powder X-ray diffraction measurements suggest that MACdCl forms a 2D layered perovskite structure and has two structural transitions at 283 and 173 K. In contrast, MACdBr and MACdI adopt 0D KSO-derived crystal structures based on isolated CdX tetrahedra and show no phase transitions down to 20 K. The contrasting crystal structures and chemical compositions in the MACdX family impact their air stabilities, investigated for the first time in this work; MACdCl is air-stable, whereas MACdBr and MACdI partially decompose when left in air. Optical absorption measurements suggest that MACdX have large optical band gaps above 3.9 eV. Room temperature photoluminescence spectra of MACdX yield broad peaks in the 375-955 nm range with full width at half-maximum values up to 208 nm. These PL peaks are tentatively assigned to self-trapped excitons in MACdX following the crystal and electronic structure considerations. The bands around the Fermi level have small dispersions, which is indicative of high charge localization with significant exciton binding energies in MACdX. On the basis of our combined experimental and computational results, MACdX and related compounds may be of interest for white-light-emitting phosphors and scintillator applications.

We report syntheses, crystal and electronic structures, and characterization of three new hybrid organic–inorganic halides (R)ZnBr 3 (DMSO), (R) 2 CdBr 4 ·DMSO, and (R)CdI 3 (DMSO) (where (R) = C 6 (CH 3 ) 5 CH 2 N(CH 3 ) 3 , and DMSO = dimethyl sulfoxide). The compounds can be conveniently prepared as single crystals and bulk polycrystalline powders using a DMSO–methanol solvent system. On the basis of the single-crystal X-ray diffraction results carried out at room temperature and 100 K, all compounds have zero-dimensional (0D) crystal structures featuring alternating layers of bulky organic cations and molecular inorganic anions based on a tetrahedral coordination around group 12 metal cations. The presence of discrete molecular building blocks in the 0D structures results in localized charges and tunable room-temperature light emission, including white light for (R)ZnBr 3 (DMSO), bluish-white light for (R) 2 CdBr 4 ·DMSO, and green for (R)CdI 3 (DMSO). The highest photoluminescence quantum yield (PLQY) value of 3.07% was measured for (R)ZnBr 3 (DMSO), which emits cold white light based on the calculated correlated color temperature (CCT) of 11,044 K. All compounds exhibit fast photoluminescence lifetimes on the timescale of tens of nanoseconds, consistent with the fast luminescence decay observed in π-conjugated organic molecules. Temperature dependence photoluminescence study showed the appearance of additional peaks around 550 nm, resulting from the organic salt emission. Density functional theory calculations show that the incorporation of both the low-gap aromatic molecule R and the relatively electropositive Zn and Cd metals can lead to exciton localization at the aromatic molecular cations, which act as luminescence centers.

The photophysical mechanism of ultrabright visible light emission in the zero-dimensional (0D) hybrid organic–inorganic material (HOIM), (DETA)­PbCl5·H2O (DETA = diethylenetriammonium), has been studied. This compound exhibits efficient room-temperature bluish white-light (WL) emission, corroborated by a high photoluminescence quantum yield (PLQY) value of 36.8 % and a Commission Internationale de l’Eclairage (CIE) color coordinates of (0.18, 0.17). Optical investigations reveal that broad-band emission containing multiple emission centers originates from both the fluorescence of the organic molecules DETA and self-trapped excitons within the [Pb2Cl10]6– inorganic bioctahedral dimers. Furthermore, an enhanced PLQY of up to 40.3% with an adjusted pure WL emission (CIE of (0.33, 0.34)) and a remarkable color rendering index of 90 was achieved through the incorporation of Mn2+ within (DETA)­PbCl5·H2O. These findings aid in understanding the photophysical properties of 0D HOIMs and preparation of new families of highly emissive materials for solid-state lighting applications.

Perovskites olar cells have recently enabledp ower conversion efficiencyc omparable to established technologies such as silicon and cadmiumt elluride.O ngoing efforts to improve the stability of halide perovskites in ambient air has yielded promising results. However,t he presence of toxic heavy elementl ead (Pb) remains am ajor concern requiring further attention. Herein, we report three new Pbfree hybrido rganic-inorganic perovskite-typeh alides based on gold (Au), (CH 3 NH 3 )AuBr 4 ·H 2 O( 1), (CH 3 NH 3 )AuCl 4 ·H 2 O( 2), and (CH 3 NH 3 )AuCl 4 (3). Hydrated compounds 1 and 2 crystallize in ab rand-new structure type featuring perovskite-derived 2D layers and 1D chains based on pseudo-octahedral AuX 6 building blocks. In contrast,t he novel crystal structure of the solvent-freec ompound 3 shows an exotic non-perovskite quasi-2D layered structure containing edge-and corner-shared AuCl 6 octahedra. The use of Au metal instead of Pb resultsi nu nprecedented low band gaps below 2.5 eV for single-layered metal chlorides and bromides. Moreover, at room temperature the three compounds show aw eak blue emission due to the electronic transition between Au-6s and Au-5d, in agreement with the density function theory (DFT) calculation results. These findings are discussed in the context of viability of Au-based halidesa sa lternatives for Pb-based halides for optoelectronic applications.