Lead-free double perovskites have been proposed as promising nontoxic photovoltaic materials for the replacement of lead perovskites. While latter ones reach remarkably high power conversion efficiencies (PCEs) above 23% in small lab devices, lead-free so far severely underperformed, with PCEs below 3% prototypical system Cs2AgBiBr6, spite considerable optimization efforts by several groups. Here, we present a detailed study Cs2AgBiBr6 thin films deposited on poly(methyl methacrylate) and...

Quasiclassical trajectory calculations of the energy transfer highly vibrationally excited benzene and hexafluorobenzene (HFB) molecules colliding with helium, argon xenon have been performed. Deactivation is found to be more efficient for HFB in accord experiment. This effect due greater number low frequency vibrational modes HFB. A correlation between parameters properties intramolecular potential found. For HFB, average energies transferred per collision given range increase energy....

Complete and detailed experimental transition probability density functions P(E′,E) have been determined for the first time collisions between a large, highly vibrationally excited molecule, toluene, several bath gases. This was achieved by applying method of kinetically controlled selective ionization (KCSI) (Paper I [J. Chem. Phys. 112, 4076 (2000), preceding article]). An optimum representation is recommended (monoexponential with parametric exponent in argument) which uses only three...

New photochromic switches based on helical alkenes can quickly and efficiently be accessed by Pd-catalyzed domino reactions using a modular approach; this allows wide variability in product formation with the advantages of convergent synthetic route. The have been synthesized excellent enantioselectivity their switching properties assessed stimulation nanosecond laser pulses at two different wavelengths over 1000 cycles.

Molecular switches based on helical tetrasubstituted alkenes, substituted with either electron-withdrawing (CF(3), F, CN; 2a-c, 3a,c) or -donating substituents (Me, OMe; 2d,e), have been synthesized from acyclic precursors 4 and 5 in a domino carbopalladation/Stille reaction. This palladium-catalyzed process allowed the rapid assembly of two C-C bonds, six-membered rings, double bond completely diastereoselective fashion. The electronic effects overall switching were investigated by...

The so-called S* state has been suggested to play an important role in the photophysics of beta-carotene and other carotenoids solution photosynthetic light-harvesting complexes, yet its origin remained elusive. present experiments employing temperature-dependent steady-state absorption spectroscopy ultrafast pump-supercontinuum probe (PSCP) transient measurements demonstrate that spectral features are due vibrationally excited molecules ground electronic S(0). Characteristic signatures,...

Ultrafast broadband transient absorption spectroscopy elucidates charge carrier dynamics in the perovskite CH₃NH₃PbI₃.

Broadband transient absorption spectroscopy reveals an increased carrier recombination rate constant of low-dimensional perovskites.

Low-dimensional copper halides, such as CsCu2I3, have emerged promising LED materials featuring strongly Stokes-shifted photoluminescence with high quantum yield. Previous calculations suggest an exciton self-trapping mechanism; however, direct experimental evidence for this process is still lacking. Here, we present femtosecond UV-vis transient absorption experiments of CsCu2I3 thin films. The films were analyzed by SEM, XRD, and 133Cs/63Cu NMR crystallinity defects. Unique spectral...

Abstract Measurements of the electronic circular dichroism (CD) are highly sensitive to absolute configuration and conformation chiral molecules supramolecular assemblies have therefore found widespread application in chemical biological sciences. Here, we demonstrate an approach simultaneously follow changes CD absorption response photoexcited systems over ultraviolet−visible spectral range with 100 fs time resolution. We apply concept polyfluorene copolymer thin films track their...

Silver iodobismuthate thin films obtained from mixtures of AgI and BiI3 have been frequently suggested as promising alternatives for lead-based perovskite materials in photovoltaic applications. Here, we investigated (AgI)x(BiI3)y with stoichiometric ratios (x/y) 3:1, 2:1, 1:1, 1:2 produced via a low-temperature (<100 °C) spin coating process AgI/BiI3 solutions dimethyl sulfoxide. Several critical observations on the basis ultrafast broadband UV–vis transient absorption spectroscopy...

The ultrafast internal conversion (IC) dynamics of aldehyde-substituted apocarotenoids (n'-apo-beta-caroten-n'-als with n=4, 8 and 12) have been investigated in a systematic variation conjugation length solvent polarity using time-resolved femtosecond transient absorption spectroscopy. After excitation to the S2 state different excess energies, subsequent intramolecular were at several probe wavelengths covering S0-->S2 S1/ICT-->Sn bands. Time constants tau1 for process S1/ICT-->S0...

The ultrafast photoinjection and subsequent relaxation steps of the indoline dye D149 were investigated in detail for a mesoporous electrodeposited ZnO thin film compared with experiments on sintered TiO2 ZrO2 films, all contact air, using pump–supercontinuum probe (PSCP) transient absorption spectroscopy range 370–770 nm. efficiently injects electrons into surface time constants from ≤70 fs (time-resolution-limited) up to 250 fs, without presence slower components. Subsequent spectral...

Abstract A highly efficient palladium‐catalyzed fourfold tandem‐domino reaction consisting of two carbopalladation and CH‐activation steps was developed for the synthesis types tetrasubstituted alkenes 3 6 with intrinsic helical chirality starting from substrates 1 4 , respectively. sixfold also by including a Sonogashira reaction. 20 compounds different substitution patterns were prepared yields up to 97 %. Structure elucidation X‐ray crystallography confirmed alkene moieties....

We investigated the ultrafast carrier dynamics and phonon relaxation of CVD-grown monolayer 9-layer graphene on a quartz substrate. Excitation was performed at 400 800 nm. The normalized change in optical density ΔOD probed over range 260–640 nm (1.94–4.77 eV), reaching down into region graphene's Fano resonance, previously not femtosecond broadband pump–probe experiments. Time constants 160 fs 4 ps were found assigned to carrier–optical scattering slower processes, respectively....

The relaxation dynamics of the dye D35 has been characterized by transient absorption spectroscopy in acetonitrile and on TiO2 ZrO2 thin films. In acetonitrile, upon photoexcitation via S0 → S1 transition, we observed ultrafast solvation with subpicosecond time constants. Subsequent decay excited state (ESA) band a 7.1 ps constant is tentatively assigned to structural state, spectral 203 results from internal conversion (IC) back S0. On TiO2, fast (<90 fs) electron injection into conduction...

We present an investigation of the ultrafast charge carrier dynamics for one-third metal-deficient lead-free perovskite (CH3NH3)3Bi2I9 on mesoporous TiO2. Excitation at 400 or 505 nm leads to characteristic second-derivative-type spectral features in transient absorption spectra, suggesting substantial contributions bound excitons, contrast widely used lead-based perovskites. The immediate appearance broad NIR is assigned TiO2 conduction band electrons formed by instantaneous dissociation a...

Organic‐inorganic halocuprates(I) form a promising class of light‐emitting materials with high photoluminescence (PL) quantum yield. However, the understanding their emission properties and PL mechanism is still limited. Here, we investigate thin films bis(tetrapropylammonium) hexa‐µ‐bromo‐tetrahedro‐tetracuprate(I), [N(C3H7)4]2[Cu4Br6], which has zero‐dimensional (0D) molecular salt structure containing [Cu4Br6]2− ions. The compound shows bright orange PL, consisting two bands, yield about...

The method of kinetically controlled selective ionization (KCSI) for investigating collisional energy transfer in highly vibrationally excited molecules is presented detail. In this first paper a series the focus on key concepts and technical realization KCSI experiments to provide common basis following reports our available results studies vibrational relaxation variety larger molecules. technique directly monitors energetic position shape population distributions g(E,t) during process by...

The ultrafast excited-state dynamics of two carbonyl-containing carotenoids, 12'-apo-beta-caroten-12'-al and 8'-apo-beta-caroten-8'-al, have been investigated by transient absorption spectroscopy in a systematic variation solvent polarity temperature. In most the experiments, was excited at 430 nm 8'-apo-beta-caroten-8'-al 445 or 450 via S0 --> S2 (11Ag- 11Bu+) transition. were then probed 860 for 890 900 8'-apo-beta-caroten-8'-al. temporal evolution all signals measured this work can be...

The ultrafast internal conversion dynamics of 12′-apo-β-carotenoic-12′-acid (12′CA), 10′-apo-β-carotenoic-10′-acid (10′CA) and 8′-apo-β-carotenoic-8′-acid (8′CA) have been investigated by femtosecond pump–probe spectroscopy. three apocarotenoic acids were excited to the S2 state with different excess energies. Time constants τ1 for IC process S1/ICT → S0 measured probing at 390 nm (S0 S2), 575 (S1/ICT Sn), 850, 860 890 (S2 Sn S0). In nonpolar solvents, observed reduction values increasing...

Ultrafast transient broadband absorption spectroscopy based on the Pump-Supercontinuum Probe (PSCP) technique has been applied to characterize excited state dynamics of newly-synthesized artificial β-carotene derivative 13,13'-diphenyl-β-carotene in wavelength range 340-770 nm with ca. 60 fs cross-correlation time after excitation S(2) state. The influence phenyl substitution at polyene backbone investigated different solvents by comparing internal conversion (IC) processes S(2)→ S(1) and...

The relaxation dynamics of the indoline dye D149, a well-known sensitizer for photoelectrochemical solar cells, have been extensively characterized in various organic solvents by combining results from ultrafast pump-supercontinuum probe (PSCP) spectroscopy, transient UV-pump VIS-probe time-correlated single-photon counting (TCSPC) measurements as well steady-state absorption and fluorescence. In spectra, position maximum shows only weak solvent dependence, whereas fluorescence Stokes shift...

We investigated photoinduced primary charge transfer processes of the sensitizer E6 on TiO2 without solvent and in contact with organic acetonitrile ionic liquid 1-ethyl-3-methylimidazolium tetracyanoborate [C2mim](+)[B(CN)4](-) using transient absorption spectroscopy, spectroelectrochemistry, DFT/TDDFT calculations. E6, which belongs to a family triarylamine dyes for solar cell applications, features two peripheral units are connected via diether spacer groups core chromophore designed act...