Two-dimensional (2D) hybrid perovskites are stoichiometric compounds consisting of alternating inorganic metal-halide sheets and organoammonium cationic layers. This materials class is widely tailorable in composition, structure, dimensionality providing an intriguing playground for the solid-state chemistry physics communities to uncover structure–property relationships. In this Perspective, we describe semiconducting 2D containing lead tin halide frameworks. these perovskites, charges...

Quantum and dielectric confinement effects in Ruddlesden-Popper 2D hybrid perovskites create excitons with a binding energy exceeding 150 meV. We exploit the large exciton to study carrier dynamics as well electron–phonon coupling (EPC) using absorption photoluminescence (PL) spectroscopies. At temperatures <75 K, we resolve splitting of excitonic PL into multiple regularly spaced resonances every 40–46 meV, consistent EPC phonons located on organic cation. also 14 meV spacing, accord mixed...

We use solid-state methods to synthesize single crystals of perovskite-phase cesium lead iodide (${\gamma}$-CsPbI3) that are kinetically stable at room temperature. Single crystal X-ray diffraction characterization shows the compound is orthorhombic with GdFeO3 structure Unlike conventional semiconductors, optical absorption and joint density-of-states bulk ${\gamma}$-CsPbI3 greatest near band edge decreases beyond Eg for least 1.9 eV. Bulk does not show an excitonic resonance has gap...

Despite the tremendous interest in halide perovskite solar cells, structural reasons that cause all-inorganic CsPbI3 to be unstable at room temperature remain mysterious, especially since many tolerance-factor-based approaches predict should stable as a perovskite. Here single-crystal X-ray diffraction and pair distribution function (PDF) measurements characterize bulk from 100 295 K elucidate its thermodynamic instability. While Cs occupies single site 150 K, it splits between two sites 175...

We use scanning photocurrent microscopy and time-resolved microwave conductivity to measure the diffusion of holes electrons in a series lead bromide perovskite single crystals, APbBr3, with A = methylammonium (MA), formamidinium (FA), Cs. find that length (LDh+ ∼ 10–50 μm) is on average an order magnitude longer than (LDe– 1–5 μm), regardless A-type cation or applied bias. Furthermore, we observe weak dependence LD across A-cation MA > FA When considering role halide, MAPbBr3 comparable...

We synthesize and characterize derivatives of the two-dimensional hybrid perovskite (2DHP) phenethylammonium lead iodide ((PEA)2PbI4) in which para H on cation is replaced with F, Cl, CH3, or Br. These substitutions increase length but leave cross-sectional area unchanged, resulting structurally similar PbI42- frameworks increasing interlayer spacing. Longer cations result broader, blue-shifted excitonic absorption spectra reduced eliminated structure, indicating greater energetic disorder....

Using a combination of scanning photocurrent microscopy (SPCM) and time-resolved microwave conductivity (TRMC) measurements, we monitor the diffusion recombination photoexcited charges in CH3NH3PbI3 perovskite single crystals. The majority carrier type was controlled by growing crystals presence or absence air, allowing lengths electrons (LDe–) holes (LDh+) to be directly imaged with SPCM (LDe– = 10–28 μm, LDh+ 27–65 μm). TRMC measurements reveal photogenerated mobility (μh + μe) 115 ± 15...

The ability to continuously tune the band gap of a semiconductor allows its optical properties be precisely tailored for specific applications. We demonstrate that halide perovskite CsPbBr3 can widened through homovalent substitution Sr2+ Pb2+ using solid-state synthesis, creating material with formula CsPb1-xSrxBr3 (0 ≤ x 1). and form solid solution in CsPb1-xSrxBr3. Pure has 2.29(2) eV, which increases 2.64(3) eV CsPb0.25Sr0.75Br3. increase is clearly visible color change materials also...

We report a family of two-dimensional hybrid perovskites (2DHPs) based on phenethylammonium lead iodide ((PEA)2PbI4) that show complex structure in their low-temperature excitonic absorption and photoluminescence (PL) spectra as well hot exciton PL. replace the 2-position (ortho) H phenyl group PEA cation with F, Cl, or Br to systematically increase cation's cross-sectional area mass study changes structure. These single atom substitutions substantially change observable number spacing...

We report large-area, flexible, high-speed analog and digital colloidal CdSe nanocrystal integrated circuits operating at low voltages. Using photolithography a newly developed process to fabricate vertical interconnect access holes, we scale down device dimensions, reducing parasitic capacitances increasing the frequency of circuit operation, up fabrication over 4 in. flexible substrates. demonstrate amplifiers with ∼7 kHz bandwidth, ring oscillators <10 μs stage delays, NAND NOR logic gates.

Passivating surface defects and controlling the carrier concentration mobility in quantum dot (QD) thin films is prerequisite to designing electronic optoelectronic devices. We investigate effect of introducing indium CdSe QD on dark photogenerated lifetime using field-effect transistor (FET) time-resolved microwave conductivity (TRMC) measurements. evaporate ranging from 1 11 nm thickness top approximately 40 thick thiocyanate-capped anneal at 300 °C densify drive diffusion through films....

The authors successfully dope the magnetically silent double perovskite semiconductor Sr2 GaSbO6 to induce ferromagnetism and tune its bandgap, with Ga3+ partially substituted by magnetic trivalent cation Mn3+ , in a rigid ordering Sb5+ . new ferromagnetic semiconducting Ga1-x Mnx SbO6 perovskite, which crystallizes tetragonal symmetry (space group I4/m) has tunable temperature suggests that ion doping of perovskites is productive avenue toward obtaining materials for application...

We develop a hybrid ligand exchange process to enhance both mobility and lifetime of carriers in nanocrystal thin films.

Colloidal semiconductor nanocrystals (NCs) are a promising materials class for solution-processable, next-generation electronic devices. However, most high-performance devices and circuits have been achieved using NCs containing toxic elements, which may limit their further device development. We fabricate high mobility CuInSe2 NC field-effect transistors (FETs) solution-based, post-deposition, sequential cation exchange process that starts with electronically coupled, thiocyanate...

Strongly coupled, epitaxially fused colloidal nanocrystal (NC) solids are promising solution-processable semiconductors to realize optoelectronic devices with high carrier mobilities. Here, we demonstrate sequential, solid-state cation exchange reactions transform connected PbSe NC thin films into Cu2Se nanostructured thin-film intermediates and then successfully achieve zinc-blende, CdSe wide epitaxial necking along {100} facets. Transient photoconductivity measurements probe transport at...

Magnetically active atomic distances may impact the magnetic ordering in a given system both directly and indirectly. We synthesize three novel quasi-one-dimensional organic–inorganic hybrid cobalt chloride chain compounds (CH3NH3CoCl3, CH(NH2)2CoCl3, C(NH2)3CoCl3) characterize their thermodynamic properties. These materials crystallize hexagonal perovskite-type structure consisting of chains face-sharing Co–Cl octahedra separated by respective organic cation. Temperature- field-dependent...

We find evidence for the formation and relaxation of large exciton polarons in 2D organic-inorganic hybrid perovskites. Using ps-scale time-resolved photoluminescence within phenethylammonium lead iodide family compounds, we identify a red shifting emission that associate with polaron time scales 3-10 ps. Atomic substitutions cation allow local control over structure inorganic lattice, show structural differences among materials strongly influence process, revealing binding energy grows...

This work uses the photodissociation of acetyl chloride to assess utility a recently proposed impulsive model when dissociation occurs on an excited electronic state that is not repulsive in Franck-Condon region. The explicitly includes average over vibrational quantum states it calculates impact parameter for fission C-Cl bond, as well distribution thermal energy photolytic precursor. experimentally determined stability resulting radical subsequent key observable allows us test model's...

We synthesize and characterize the magnetic thermodynamic properties of quasi one-dimensional organic-inorganic hybrid ANiCl3 compounds [A = N(CH3)4+, CH3NH3+, (CH3)2NH2+, C(NH2)3+, CH(NH2)2+]. Additionally, crystal structure (CH3)2NH2NiCl3 is reported. These materials possess chains face-sharing NiCl6 octahedra in a triangular array. The run one direction are separated from another by organic cations different sizes geometries. In accordance with 90° superexchange model, we find that nature...

We synthesize four novel quasi-one-dimensional organic-inorganic hybrid iron chloride compounds (CH

The design of new chiral materials usually requires stereoselective organic synthesis to create molecules with centers. Less commonly, achiral can self-assemble into materials, despite the absence intrinsic molecular chirality. Here, we demonstrate assembly high-symmetry a van der Waals structure by synthesizing crystals C60(SnI4)2 from icosahedral buckminsterfullerene (C60) and tetrahedral SnI4 through spontaneous self-assembly. tetrahedra template Sn atoms cubic three-connected net SrSi2...

Bulk CsEuBr$_3$ and CsEuCl$_3$ are experimentally shown to be magnetic semiconductors that order antiferromagnetically at Neel temperatures of 2.0 K 1.0 respectively. Given nanoparticles thin films have been reported ferromagnetically a similar temperature, our observation antiferromagnetic ordering in expands the possible applications halide perovskites now include spintronic devices where both ferromagnetic can fabricated from single material. The conclusion used as switchable material is...

We use a combination of crossed laser-molecular beam scattering experiments and velocity map imaging to investigate the three primary photodissociation channels chloroacetone at 193 nm: C–Cl bond photofission yielding CH3C(O)CH2 radicals, C–C CH3CO CH2Cl products, C–CH3 resulting in CH3 C(O)CH2Cl products. Improved analysis data previously reported by our group quantitatively identifies contribution this latter channel. introduce forward convolution procedure identify portion signal, derived...