Unraveling the Compositional Heterogeneity and Carrier Dynamics of Alkali Cation Doped 3D/2D Perovskites with Improved Stability.

Preventing the degradation of hybrid perovskite by humid air remains a challenge for their future commercial utilization. 3D/2D perovskites with hierarchical architecture have attracted significant attention due to their promising power conversion efficiency (PCE) and device stability. Here, we report novel 3D/2D planar bi-layer perovskite obtained by growing 2D Ruddlesden-Popper layer on top of 3D rubidium (Rb)-doped triple-cation perovskite.

Photodynamics of Asymmetric Di-Iron-Cyano Hydrogenases Examined by Time-Resolved Mid-Infrared Spectroscopy.

Two anionic asymmetric Fe-Fe hydrogenase model compounds containing a single cyano (CN) and five carboxyl (CO) ligands, [EtN][Fe(μ-SCH)(CO)(CN)] and [EtN][Fe(μ-SCH)(CO)(CN)], dissolved in room-temperature acetonitrile, are examined. The molecular asymmetry affects the redox potentials of the central iron atoms, thus changing the photophysics and possible catalytic properties of the compounds. Femtosecond ultraviolet excitation with mid-infrared probe spectroscopy of the model compounds was employed to better understand the ultrafast dynamics of the enzyme-active site.

Carrier mobility of silicon by sub-bandgap time-resolved terahertz spectroscopy.

Low density charge mobility from below bandgap, two-photon photoexcitation of bulk silicon (Si) is interrogated using time-resolved terahertz spectroscopy (TRTS). Total charge mobility is measured as a function of excitation frequency and fluence (charge carrier density), cut angle, and innate doping levels. Frequency dependent complex photoconductivities are extracted using the Drude model to obtain average and DC-limit mobility and carrier scattering times.

Polarization Dependence of Charge Conduction in Conjugated Polymer Films Investigated with Time-Resolved Terahertz Spectroscopy.

Room temperature Time-Domain Terahertz (TDS) and Time-Resolved Terahertz (TRTS) spectroscopic methods are employed to measure carrier mobility and charge generation efficiency in thin-film semiconductor polymers. Interrogation of the dependence on excitation and probe polarizations yields insight into the underlying material properties that guide charge transport. We apply THz polarization anisotropy probes to analyze charge conduction in preparations of the copolymer PCDTPT, consisting of alternating cyclopenta-dithiophene (donor) and thiadiazolo-pyridine (acceptor) units.

Photodynamics of [FeFe]-Hydrogenase Model Compounds with Bidentate Heterocyclic Ligands.

Two asymmetrically structured model compounds for the hydrogen-generating [Fe-Fe]-hydrogenase active site were investigated to determine the ultrafast photodynamics, structural intermediates, and photoproducts compared to more common symmetric di-iron species. The bidentate-ligand-containing compounds studied were Fe(μ-SCH)(CO)(bipy), , and Fe(μ-SCH)(CO)(phen), , in dilute room temperature acetonitrile solution and low-temperature 2Me-THF matrix isolation using static FTIR difference and time-resolved infrared spectroscopic methods (TRIR). Ultraviolet-visible spectra were also compared to time-dependent density functional theory (TD-DFT) to ascertain the orbital origins of long wavelength electronic absorption features.