Guanidinium Iodide Research Articles

Efficient Catalysts of Acyclic Guanidinium Iodide for the Synthesis of Cyclic Carbonates from Carbon Dioxide and Epoxides under Mild Conditions

We have studied the synthesis of five-membered cyclic carbonates through the cycloaddition of CO2 to epoxides by using acyclic guanidinium salts. We have found that the cycloaddition reactions proceed smoothly at ordinary temperatures and pressures and result in good yields when acyclic guanidinium iodides are employed as catalysts. Both cation moiety and anion moiety of the guanidinium salts play important roles in their catalytic activity. It is essential to have active hydrogens on the cation moiety as well as an iodide ion as the anion moiety so as to achieve good catalytic activity. Guanidinium iodides with three or more active hydrogens give cyclic carbonates in high yields in polar solvents such as 1-methylpyrrolidin-2-one, whereas the guanidinium iodides with one or two active hydrogens show good catalytic activity in less polar solvents such as 2-methyltetrahydrofuran.

Atomic-level passivation mechanism of ammonium salts enabling highly efficient perovskite solar cells

The high conversion efficiency has made metal halide perovskite solar cells a real breakthrough in thin film photovoltaic technology in recent years. Here, we introduce a straightforward strategy to reduce the level of electronic defects present at the interface between the perovskite film and the hole transport layer by treating the perovskite surface with different types of ammonium salts, namely ethylammonium, imidazolium and guanidinium iodide. We use a triple cation perovskite formulation containing primarily formamidinium and small amounts of cesium and methylammonium. We find that this treatment boosts the power conversion efficiency from 20.5% for the control to 22.3%, 22.1%, and 21.0% for the devices treated with ethylammonium, imidazolium and guanidinium iodide, respectively. Best performing devices showed a loss in efficiency of only 5% under full sunlight intensity with maximum power tracking for 550 h. We apply 2D- solid-state NMR to unravel the atomic-level mechanism of this passivation effect.

Perovskite Solar Cells Yielding Reproducible Photovoltage of 1.20 V

High photovoltages and power conversion efficiencies of perovskite solar cells (PSCs) can be realized by controlling the undesired nonradiative charge carrier recombination. Here, we introduce a judicious amount of guanidinium iodide into mixed-cation and mixed-halide perovskite films to suppress the parasitic charge carrier recombination, which enabled the fabrication of >20% efficient and operationally stable PSCs yielding reproducible photovoltage as high as 1.20 V. By introducing guanidinium iodide into the perovskite precursor solution, the bandgap of the resulting absorber material changed minimally; however, the nonradiative recombination diminished considerably as revealed by time-resolved photoluminescence and electroluminescence studies. Furthermore, using capacitance-frequency measurements, we were able to correlate the hysteresis features exhibited by the PSCs with interfacial charge accumulation. This study opens up a path to realize new record efficiencies for PSCs based on guanidinium iodide doped perovskite films.

Perovskite Solar Cells Yielding Reproducible Photovoltage of 1.20 V.

High photovoltages and power conversion efficiencies of perovskite solar cells (PSCs) can be realized by controlling the undesired nonradiative charge carrier recombination. Here, we introduce a judicious amount of guanidinium iodide into mixed-cation and mixed-halide perovskite films to suppress the parasitic charge carrier recombination, which enabled the fabrication of >20% efficient and operationally stable PSCs yielding reproducible photovoltage as high as 1.20 V. By introducing guanidinium iodide into the perovskite precursor solution, the bandgap of the resulting absorber material changed minimally; however, the nonradiative recombination diminished considerably as revealed by time-resolved photoluminescence and electroluminescence studies. Furthermore, using capacitance-frequency measurements, we were able to correlate the hysteresis features exhibited by the PSCs with interfacial charge accumulation. This study opens up a path to realize new record efficiencies for PSCs based on guanidinium iodide doped perovskite films.

Morphology and structure improvement of the hybrid CH3NH3PbI3 perovskite film via external doping

The optoelectronic properties of perovskite films are closely related to their quality. Herein, we report the doping of guanidinium iodide (C(NH2)3I) organic into CH3NH3PbI3 perovskite thin films and reveal the enhancement of both morphology and structure of the perovskite films by doping with C(NH2)3I in the range of 0 to 25%. Nuclear magnetic resonance is utilized to determine the molecular structure of the synthesized C(NH2)3I and grazing-incidence X-ray diffraction is employed to characterize the lattice structure of doped perovskite films. Furthermore, doped CH3NH3PbI3 perovskite films with different amounts of C(NH2)3I is also investigated by X-ray photoelectron spectroscopy and scanning electron microscopy. It is found that the C(NH2)3I dopant mainly assembles on the surface region of the pristine CH3NH3PbI3 perovskite film. In the end, 5% C(NH2)3I to CH3NH3PbI3 perovskite film is found to be the doping ratio resulting in the best film structure and surface morphology.

Guanidinium iodide-catalyzed oxidative α-nitroalkylation of β-ketoamides.

Oxidative nitroalkylation of β-ketoamides and nitroalkanes, mediated by hypoiodide generated from tert-butyl hydrogen peroxide and a catalytic amount of guanidinium iodide, afforded the corresponding α-nitroalkyl-β-ketoamides in up to 97% yield.

Origin of spontaneous polarization and reconstructive phase transition in guanidinium iodide

Download options Please wait... Supplementary files Crystal structure data TXT (76K) Article information DOI https://doi.org/10.1039/C3CE26979E Article type Paper Submitted 07 Dec 2012 Accepted 25 Jan 2013 First published 25 Jan 2013 Download Citation CrystEngComm, 2013,15, 4617-4623 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Origin of spontaneous polarization and reconstructive phase transition in guanidinium iodide M. Szafrański and M. Jarek, CrystEngComm, 2013, 15, 4617 DOI: 10.1039/C3CE26979E To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Social activity Tweet Share Search articles by author Marek Szafrański Marcin Jarek

Managing wetting behavior and collection efficiency in photoelectrochemical devices based on water electrolytes; improvement in efficiency of water/iodide dye sensitised cells to 4%

We have fabricated Dye Sensitised Solar Cells (DSSCs) using only water as the solvent and guanidinium iodide–iodine as the redox couple that operate at 4% energy efficiency under 1-sun illumination. This result is ∼5 times higher than the best previously reported values. We show that it is critical to facilitate the wetting of water electrolytes into the mesoporous TiO2 dye films, especially when using hydrophobic dyes. We show chenodeoxycholic acid to be a good surfactant for this purpose. By separate variation of iodide and iodine concentrations in series of cells we show that the optimum concentrations for water based DSSCs are quite different from those used in organic electrolytes. We argue that this is due to the much lower stability constant of tri-iodide in water, relative to organic solvent. Finally we also vary the TiO2 thickness and pore structure to achieve the above stated efficiency.

Crystal structure of (R)-N,N′,N′,N″,N″-pentamethyl-N-(1-phenylethyl)- guanidinium iodide, [C14H24N3

Crystal structure of (R)-N,N′,N′,N″,N″-pentamethyl-N-(1-phenylethyl)- guanidinium iodide, [C14H24N3

Crystal structure of (R)-N,N',N',N"-pentamethyl-N-(1-phenylethyl)- guanidinium iodide, [C14H24N3

Crystal structure of (R)-N,N',N',N"-pentamethyl-N-(1-phenylethyl)- guanidinium iodide, [C14H24N3

1H NMR Studies on the Dynamics of Planar [C(NH2)3]+ Cations in the Crystal of Various Guanidinium Salts

AbstractThe temperature dependences of 1H NMR spin‐lattice relaxation times and 1H NMR second moments were observed for guanidinium chloride, bromide, iodide, thiocyanate, nitrate, and perchlorate. The results of the NMR experiments carried out with the crystals of these compounds except the last one can be interpreted in terms of the C3 reorientation of the cation about its symmetry axis. The solid‐solid phase transition at 454 K reported for guanidinium perchlorate could be resolved into two phase transitions taking place successively at 450 and 452 K. In the low temperature phase of this salt, the C3 reorientation of the cation is activated. The occurrence of cationic self‐diffusion in the high temperature phase was confirmed by the measurements of 1H NMR relaxation times. The NMR motional parameters are evaluated for these cationic motions in the present salts. The phase transition temperature of guanidinium iodide was strongly depended on the grain size of the sample employed. Guanidinium bromide yielded a single 81Br NQR line at room temperature indicating that all bromide ions in the crystal are crystallographically equivalent in agreement with the results of X‐ray analysis.

Pyroelectric, dielectric, thermal, piezoelectric, electro-optical, elastic, and thermoelastic properties of hexagonal guanidinium iodide, C(NH2)3I

Article Pyroelectric, dielectric, thermal, piezoelectric, electro-optical, elastic, and thermoelastic properties of hexagonal guanidinium iodide, C(NH2)3I was published on October 1, 1984 in the journal Zeitschrift für Kristallographie - Crystalline Materials (volume 167, issue 1-4).

Reactions of S-alkyl-NN-disubstituted thioamide salts. Part 3. Thiocarbamoyl cyanide derivatives

Two tetrahedrally substituted thiocarbamoyl cyanide derivatives have been found to undergo rearrangement on heating with morpholine. Bis(methylthio)-4-morpholinoacetonitrile (7) and methylthio-4-morpholinomalononitrile (8) were synthesised from SS′-dimethyl-N-(3-oxapentamethylene)dithiocarbamidium iodide (4), and, with morpholine gave tris-(3-oxapentamethylene)guanidinium thiocyanate (5; X = SCN) and reduction componds. The salt (4) also reacted with morpholine to give the guanidinium iodide (5; X = I) and with hydrogen sulphide giving dimethyl trithiocarbonate.