A Switchable High-Sensitivity Photodetecting and Photovoltaic Device with Perovskite Absorber

Amplified photocurrent gain has been obtained by photodiodes of inorganic semiconductors such as GaAs and Si. The avalanche photodiode, developed for high-sensitivity photodetectors, requires an expensive vapor-phase epitaxy manufacture process and high driving voltage (50-150 V). Here, we show that a low-cost solution-processed device using a planar-structured ferroelectric organo-lead triiodide perovskite enables light detection in a large dynamic range of incident power (10(-7)-10(-1) W cm(-2)) by switching with small voltage (-0.9 to +0.5 V). The device achieves significantly high external quantum conversion efficiency (EQE) up to 2.4 × 10(5)% (gain value of 2400) under weak monochromatic light. On a single dual-functional device, incident small power (0.2-100 μW cm(-2)) and medium to large power (>0.1 mW cm(-2)) are captured by reverse bias and forward bias modes, respectively, with linear responsivity of current. For weak light detection, the device works with a high responsivity value up to 620 A W(-1).

Syntheses, crystal structures, luminescent and magnetic properties of two molecular solids containing naphthylmethylene triphenylphosphinium cations and tetra(isothiocyanate)cobalt(II) dianion

The reaction of CoCl2 with the naphthalene methylated triphenylphosphinium bromide [n-NAPMeTPP]Br (n=1, 2) and KSCN, in a methanolic medium at ambient temperature, leads to the self-assembly formation of hybrid 2:1 organic-inorganic molecular solids, [1-NAPMeTPP]2[Co(NCS)4](1) and [2-NAPMeTPP]2[Co(NCS)4](2) ([NAPMeTPP](+)=(naphthylmethylene)(triphenyl)phosphinium), which have been characterized by elemental analyses, IR spectroscopy, UV-Vis spectra, ESI-MS, molar conductivity and single-crystal X-ray diffraction structural analyses. Compound 1 crystallizes in the orthorhombic space group Pna21, while 2 does in the monoclinic space group C2/c. The cations form a dimer through the weak intermolecular C-H⋯π interactions in 1 and π⋯π interaction in 2, while the anion and cation are linked by the C-H⋯S hydrogen bond in 1. Two molecular solids show dual functionalities: (1) the broad fluorescence emission around 400nm in the solid state at room temperature; (2) the weak antiferromagnetic coupling behavior.

Interfacial control toward efficient and low-voltage perovskite light-emitting diodes

High-performance perovskite light-emitting diodes are achieved by an interfacial engineering approach, leading to the most efficient near-infrared devices produced using solution-processed emitters and efficient green devices at high brightness conditions.

Synthesis, crystal structure, vibrational spectroscopy, optical properties and theoretical studies of a new organic-inorganic hybrid material: [((CH3)2NH2)(+)]6·[(BiBr6)(3-)]2

A new organic-inorganic hybrid material, [((CH3)2NH2)(+)]6·[(BiBr6)(3-)]2, has been synthesized and characterized by X-ray diffraction, FT-IR, Raman spectroscopy and UV-Visible absorption. The studied compound crystallizes in the triclinic system, space group P1¯ with the following parameters: a=8.4749(6)(Å), b=17.1392(12)(Å), c=17.1392(12)(Å), α=117.339(0)°, β=99.487(0)°, γ=99.487(0)° and Z=2. The crystal lattice is composed of a two discrete (BiBr6)(3-) anions surrounded by six ((CH3)2NH2)(+) cations. Complex hydrogen bonding interactions between (BiBr6)(3-) and organic cations from a three-dimensional network. Theoretical calculations were performed using density functional theory (DFT) for studying the molecular structure, vibrational spectra and optical properties of the investigated molecule in the ground state. The full geometry optimization of designed system is performed using DFT method at B3LYP/LanL2DZ level of theory using the Gaussian03. The optimized geometrical parameters obtained by DFT calculations are in good agreement with single crystal XRD data. The vibrational spectral data obtained from FT-IR and Raman spectra are assigned based on the results of the theoretical calculations. The energy and oscillator strength calculated by Time-Dependent Density Functional Theory (TD-DFT) results complements with the experimental findings. The simulated spectra satisfactorily coincide with the experimental UV-Visible spectrum. The results show good consistent with the experiment and confirm the contribution of metal orbital to the HOMO-LUMO boundary.

A layered hybrid perovskite solar-cell absorber with enhanced moisture stability

Two-dimensional hybrid perovskites are used as absorbers in solar cells. Our first-generation devices containing (PEA)2(MA)2[Pb3I10] (1; PEA=C6H5(CH2)2NH3(+), MA=CH3NH3(+)) show an open-circuit voltage of 1.18 V and a power conversion efficiency of 4.73%. The layered structure allows for high-quality films to be deposited through spin coating and high-temperature annealing is not required for device fabrication. The 3D perovskite (MA)[PbI3] (2) has recently been identified as a promising absorber for solar cells. However, its instability to moisture requires anhydrous processing and operating conditions. Films of 1 are more moisture resistant than films of 2 and devices containing 1 can be fabricated under ambient humidity levels. The larger bandgap of the 2D structure is also suitable as the higher bandgap absorber in a dual-absorber tandem device. Compared to 2, the layered perovskite structure may offer greater tunability at the molecular level for material optimization.

Photovoltaics. Interface engineering of highly efficient perovskite solar cells

Advancing perovskite solar cell technologies toward their theoretical power conversion efficiency (PCE) requires delicate control over the carrier dynamics throughout the entire device. By controlling the formation of the perovskite layer and careful choices of other materials, we suppressed carrier recombination in the absorber, facilitated carrier injection into the carrier transport layers, and maintained good carrier extraction at the electrodes. When measured via reverse bias scan, cell PCE is typically boosted to 16.6% on average, with the highest efficiency of ~19.3% in a planar geometry without antireflective coating. The fabrication of our perovskite solar cells was conducted in air and from solution at low temperatures, which should simplify manufacturing of large-area perovskite devices that are inexpensive and perform at high levels.

Thermochromic effects in a Jahn-Teller active CuCl(4-)6 layered hybrid system

The hybrid material copper (II) tetrachloro-bis(phenyl ethyl ammonium) (C6H5CH2CH2NH3)2CuCl4, or PEACuCl, has been investigated by temperature-dependent spectroscopic absorption experiments. The absorption bands observed in the near-infrared region (1.3-1.9 eV) generally exhibit redshifts with increasing temperature. The temperature-induced energy shifts of the spectral components are shown to be consistently related to temperature-induced Cu-Cl bond length changes. Additionally, the thermochromic color change is caused by a charge transfer band edge redshifting (in the visible region 2.0-2.8 eV) with increasing temperature. By comparison with similar Cu-based systems, it is suggested that this shift is caused by broadening and strengthening of the band.

Reversible and irreversible chemisorption in nonporous-crystalline hybrids

The tools of synthetic chemistry allow us to fine-tune the reactivity of molecules at a level of precision not yet accessible with inorganic solids. We have investigated hybrids that couple molecules to the superior thermal and mechanical properties of solids. Herein we present, to the best of our knowledge, the first demonstration of reactivity between hybrid perovskites and substrates. Reaction with iodine vapor results in a remarkable expansion of these materials (up to 36 % in volume) where new covalent CI bonds are formed with retention of crystallinity. These hybrids also show unusual examples of reversible chemisorption. Here, solid-state interactions extend the lifetime of molecules that cannot be isolated in solution. We have tuned the half-lives of the iodinated structures from 3 h to 3 days. These nonporous hybrids drive substrate capture and controlled release through chemical reactivity. We illustrate the strengths of the hybrid by considering radioactive iodine capture.

The organic-inorganic hybrid material 1-cyclohexylpiperazine-1,4-diium tetrachloridozincate

In the crystal structure of the title organic-inorganic hybrid material, (C10H22N2)[ZnCl4], the tetrachloridozincate anions and 1-cyclohexylpiperazine-1,4-diium dications are interconnected via N-H...Cl and C-H...Cl hydrogen bonds to form layers parallel to the (001) plane. The cyclohexyl groups from adjacent chains interdigitate, thus building the three-dimensional structure. The piperazinium and cyclohexyl rings exhibit regular spatial chair conformations. The title salt was also characterized by FT-IR and Raman spectroscopic analyses.

The electronic structure of organic-inorganic hybrid compounds: (NH₄)₂CuCl₄, (CH₃NH₃)₂CuCl₄ and (C₂H₅NH₃)₂CuCl₄

Hybrid organic-inorganic compounds are an intriguing class of materials that have been experimentally studied over the past few years because of a potential broad range of applications. The electronic and magnetic properties of three organic-inorganic hybrid compounds with compositions (NH4)2CuCl4, (CH3NH3)2CuCl4 and (C2H5NH3)2CuCl4 are investigated for the first time with density functional theory plus on-site Coulomb interaction. A strong Coulomb interaction on the copper causes a relatively weak exchange coupling within the layers of the octahedral network, in good agreement with experiment. The character of the exchange interaction (responsible for magnetic behavior) is analyzed. The calculations reveal that (C2H5NH3)2CuCl4 has the strongest Jahn-Teller (JT) distortion in comparison with the two other compounds. The easy axis of magnetization is investigated, showing a weak anisotropic interaction between inter-layer Cu(2+) ions in the (C2H5NH3)2CuCl4 structure. Orbital ordering is concluded from our partial density of states calculations: a cooperation of the JT distortion with an antiferro-distortive pattern.

Naturally Self-Assembled Nanosystems and Their Templated Structures for Photonic Applications

Self-assembly has the advantage of fabricating structures of complex functionalities, from molecular levels to as big as macroscopic levels. Natural self-assembly involves self-aggregation of one or more materials (organic and/or inorganic) into desired structures while templated self-assembly involves interstitial space filling of diverse nature entities into self-assembled ordered/disordered templates (both from molecular to macro levels). These artificial and engineered new-generation materials offer many advantages over their individual counterparts. This paper reviews and explores the advantages of such naturally self-assembled hybrid molecular level systems and template-assisted macro-/microstructures targeting simple and low-cost device-oriented fabrication techniques, structural flexibility, and a wide range of photonic applications.

6.5% efficient perovskite quantum-dot-sensitized solar cell

Highly efficient quantum-dot-sensitized solar cell is fabricated using ca. 2-3 nm sized perovskite (CH(3)NH(3))PbI(3) nanocrystal. Spin-coating of the equimolar mixture of CH(3)NH(3)I and PbI(2) in γ-butyrolactone solution (perovskite precursor solution) leads to (CH(3)NH(3))PbI(3) quantum dots (QDs) on nanocrystalline TiO(2) surface. By electrochemical junction with iodide/iodine based redox electrolyte, perovskite QD-sensitized 3.6 μm-thick TiO(2) film shows maximum external quantum efficiency (EQE) of 78.6% at 530 nm and solar-to-electrical conversion efficiency of 6.54% at AM 1.5G 1 sun intensity (100 mW cm(-2)), which is by far the highest efficiency among the reported inorganic quantum dot sensitizers.

Synthesis, characterization and phase transitions of the inorganic-organic layered perovskite-type hybrids [(C(n)H(2n+1)NH3)2PbI4], n = 7, 8, 9 and 10

Four inorganic-organic hybrid materials that consist of 2-D layers of corner-sharing lead(II) iodide octahedra separated by alkylammonium chains have been crystallized and characterized via single-crystal XRD (SCXRD). The four hybrids, represented by the general formula [(C(n)H(2n+1)NH(3))(2)PbI(4)] and abbreviated C(n)PbI, exhibit multiple reversible phase transitions for a narrow temperature range. The transition temperatures were determined with differential scanning calorimetry experiments. The number of transitions and the transition temperatures are dependant on the chain length; for n = 7 and 10, there are three transitions, and for n = 8 and 9, there are two transitions. Regardless of the number of transitions, all four compounds have identical lowest temperature phases, which have inorganic layers that are eclipsed, non-planar conformations of the alkyl ammonium chains and yellow-coloured crystals. The next highest temperature phase for three of the compounds (C(10)PbI goes through an intermediate phase first), has staggered inorganic layers, all-trans planar conformations of the chains and orange coloured crystals. The highest temperature phase for n = 8 and 10 has red-coloured crystals and shows a disordering of the alkylammonium chains over two positions and staggered inorganic layers. The high temperature phase of C(7)PbI retains its orange colour and has only increased thermal motion of its alkylammonium chain. The structure of the high temperature phase of C(9)PbI was not determined. The SCXRD structures of the various phases give clues to the structural changes that the compounds undergo at the phase transitions, which will now enable future studies of their optical and electronic properties to be better understood.

Synthesis and Characterization of New Functional Material (C6H5CNH2nNH3)2PbI4(where n=0,1,2)

The new functional material, the hybrids with molecular formula (C6H5CNH2nNH3)2PbI4(where N=0,1,2) were synthesized by reactions in solution. The influences of the reactant ratio and the reaction time on the structures of the products were investigated. The structures and the properties of the hybrids were characterized using X-ray diffraction(XRD), scanning electron microscopy (SEM) and ultraviolet&visible (UV) adsorption spectra . The effect of number of methylene, n, on the structure forming and the band gap magnitude has been studied. The results demenstrate that the number of methylene has effect both on the forming of the layered structure and on the magnitude of the band gap.

Bis(2-phenyl-ethyl-ammonium) tetra-chloridocobaltate(II)

Crystals of the title compound, (C(6)H(5)CH(2)CH(2)NH(3))(2)[CoCl(4)], were grown by the solvent-evaporation method. This inorganic-organic hybrid compound exhibits a layered structure in which isolated CoCl(4) inorganic layers alternate with bilayers of phenylethylammonium cations. Although the inorganic anion is zero-dimensional, the layered structure is stabilized via N-H⋯Cl hydrogen bonds. The CoCl(4) tetra-hedra connect to the cations through N-H⋯Cl hydrogen bonds, building a two-dimensional network extending parallel to (010).