Recent discoveries of highly efficient solar cells based on lead iodide perovskites have led to a surge in research activity understanding photo carrier generation these materials, but little is known about trap states that may be detrimental cell performance. Here we provide direct evidence for hole traps the surfaces three-dimensional (3D) CH3NH3PbI3 perovskite thin films and excitonic below optical gaps materials. The possess weak transition strengths, can populated from relaxation above...

Hybrid lead-halide perovskites have emerged as an excellent class of photovoltaic materials. Recent reports suggest that the organic molecular cation is responsible for local polar fluctuations inhibit carrier recombination. We combine low frequency Raman scattering with first-principles dynamics (MD) to study fundamental nature these fluctuations. Our observations a strong central peak in both hybrid (CH$_3$NH$_3$PbBr$_3$) and all-inorganic (CsPbBr$_3$) show anharmonic, are intrinsic...

The organic cation and its interplay with the inorganic lattice underlie exceptional optoelectronic properties of organo-metallic halide perovskites. Herein we report high-quality infrared spectroscopic measurements methylammonium lead perovskite (CH3NH3Pb(I/Br/Cl)3) films single crystals at room temperature, from which dielectric function in investigated spectral range is derived. Comparison electronic structure calculations vacuum free allows for a detailed peak assignment. We analyze...

The new family of layered organic-inorganic perovskite crystals (OIPCs) is a unique addition to the set available 2D materials. It crystalline inorganic solid that surrounded by well-ordered organic ligands, both which can be modified separately. This hybrid character endows material with an unusual degree tunability and flexibility. Here, authors present their results on synthesis extensive characterization OIPC single-crystalline bilayers (C${}_{4}$H${}_{9}$NH${}_{3}$)${}_{2}$PbI${}_{4}$....

Active control over the shape, composition, and crystalline habit of nanocrystals has long been a goal. Various methods have shown to enable postsynthesis modification nanoparticles, including use Kirkendall effect, galvanic replacement, cation or anion exchange, all taking advantage enhanced solid-state diffusion on nanoscale. In these processes, however, alteration nanoparticles requires introduction new precursor materials. Here we show that for cesium lead halide perovskite reversible...

Abstract Lead-halide perovskites have emerged as promising materials for photovoltaic and optoelectronic applications. Their significantly anharmonic lattice motion, in contrast to conventional harmonic semiconductors, presents a conceptual challenge understanding the genesis of their exceptional properties. Here we report strongly temperature dependent luminescence Stokes shift electronic spectra both hybrid inorganic lead-bromide perovskite single crystals. This behavior stands stark that...

Basic scientific interest in using a semiconducting electrode molecule-based electronics arises from the rich electrostatic landscape presented by semiconductor interfaces. Technological rests on promise that combining existing (primarily Si) with (mostly organic) molecules will result whole is larger than sum of its parts. Such hybrid approach appears presently particularly relevant for sensors and photovoltaics. Semiconductors, especially Si, present an important experimental test-bed...

Singlet fission, the conversion of a singlet excitation into two triplet excitations, is viable route to improved solar-cell efficiency. Despite active efforts understand fission mechanism, which would aid in rational design new materials, comprehensive understanding mechanistic principles still lacking. Here, we present first study crystalline hexacene which, together with tetracene and pentacene, enables elucidation trends. We characterize static transient optical absorption combine our...

Since the first report of Si-C bound organic monolayers on oxide-free Si almost two decades ago, a substantial amount research has focused studying fundamental mechanical and electronic properties these Si/molecule surfaces interfaces. This feature article covers three closely related topics, including recent advances in achieving high-density (i.e., atomic coverage >55%) Si(111) substrates, an overview progress understanding energetics hybrid systems, brief summary examples subsequent...

In understanding the emerging photovoltaic materials lead-halide perovskites, orientational dynamics of organic cations has garnered much attention, whereas framework is actual optoelectronically active component. The interplay between and inorganic moieties thus key to a complete picture linking structural electronic properties. Yet mechanism consequences this organic-inorganic coupling have largely been obscured. This work elucidates unique role dipolar cations. Frustrated competition...

Recent investigations of two-dimensional (2D) hybrid organic-inorganic halide perovskites (HHPs) indicate that their optical and electronic properties are dominated by strong coupling to thermal fluctuations. While the 2D-HHPs have been extensively studied, a comprehensive understanding electron-phonon interactions is limited because little known about structural dynamics. This partially unit cells contain many atoms. Therefore, fluctuations complex difficult elucidate in detail. To overcome...

Lead-based halide perovskite crystals are shown to have strongly anharmonic structural dynamics. This behavior is important because it may be the origin of their exceptional photovoltaic properties. The double perovskite, Cs2 AgBiBr6 , has been recently studied as a lead-free alternative for optoelectronic applications. However, does not exhibit excellent activity lead-based perovskites. Therefore, explore correlation between dynamics and properties in perovskites, investigated compared its...

Abstract Reducing the size of perovskite crystals to confine excitons and passivating surface defects has fueled a significant advance in luminescence efficiency light-emitting diodes (LEDs). However, persistent gap between optical limit electroluminescence photoluminescence colloidal nanocrystals (PeNCs) suggests that defect passivation alone is not sufficient achieve highly efficient PeNC-LEDs. Here, we present materials approach controlling dynamic nature surface. Our experimental...

Two-dimensional hybrid perovskites are currently in the spotlight of condensed matter and nanotechnology research due to their intriguing optoelectronic vibrational properties with emerging potential for light-harvesting light-emitting applications. While it is known that these natural quantum wells host tightly bound excitons, mobilities fundamental optical excitations at heart applications barely explored. Here, we directly monitor diffusion excitons through ultrafast emission microscopy...

The family of 2D Ruddlesden–Popper perovskites is currently attracting great interest the scientific community as highly promising materials for energy harvesting and light emission applications. Despite fact that these are known decades, only recently has it become apparent their optical properties driven by exciton–phonon coupling, which controlled organic spacers. However, detailed mechanism this gives rise to complex absorption spectra, subject ongoing controversy. In work we show...

We show that formamidinium-based crystals are distinct from methylammonium-based halide perovskite because their inorganic sublattice exhibits intrinsic local static disorder coexists with a well-defined average crystal structure. Our study combines terahertz-range Raman scattering single-crystal X-ray diffraction and first-principles calculations to probe the evolution of dynamics temperature in range 10-300 K. The spectra shows low-temperature, strongly affects structural phase transitions...

Aliovalent substitution is a common strategy to improve the ionic conductivity of solid electrolytes for solid-state batteries. The SbS43- by WS42- in Na2.9Sb0.9W0.1S4 leads very high 41 mS cm-1 at room temperature. While pristine Na3SbS4 crystallizes tetragonal structure, substituted cubic phase temperature based on its X-ray diffractogram. Here, we show performing pair distribution function analyses and static single-pulse 121Sb NMR experiments that short-range order remains despite change...

The anharmonic lattice dynamics of oxide and halide perovskites play a crucial role in their mechanical optical properties. Raman spectroscopy is one the key methods used to study these structural dynamics. However, despite decades research, existing interpretations cannot explain temperature dependence observed spectra. We demonstrate nonmonotonic evolution with scattering intensity present model for second-order that accounts this unique trend. By invoking low-frequency feature, we are...

Halide perovskites show great optoelectronic performance, but their favorable properties are paired with unusually strong anharmonicity. It was proposed that this combination derives from the ns2 electron configuration of octahedral cations and associated pseudo-Jahn-Teller effect. We such not a prerequisite for anharmonicity low-energy lattice dynamics encountered in these materials. combine X-ray diffraction, infrared Raman spectroscopies, molecular to contrast CsSrBr3 those CsPbBr3, two...

Electronic transport across n-Si-alkyl monolayer/Hg junctions is, at reverse and low forward bias, independent of alkyl chain-length from 18 down to 1 or 2 carbons! This further recent results indicate that electron is minority, rather than majority carrier-dominated, occurs via generation recombination, (the earlier assumed) thermionic emission and, as such insensitive interface properties. The (m)ethyl show binding organic molecules directly semiconductors provides semiconductor/metal...

Halide perovskite (HP) semiconductors exhibit unique strong coupling between the electronic and structural dynamics. We use Raman polarization-orientation (PO) measurements ab initio molecular dynamics (AIMD) to investigate origin temperature evolution of anharmonicity throughout tetragonal phase $\mathrm{C}{\mathrm{H}}_{3}\mathrm{N}{\mathrm{H}}_{3}\mathrm{Pb}{\mathrm{I}}_{3}$. PO reveal a soft modelike spectral feature. This mode shows an unusual continuous increase in damping with which is...

Basic understanding of the driving forces ion conduction in solids is critical to development new solid-state conductors. Physical limited due strong deviations from harmonic vibrational dynamics these systems that are difficult characterize experimentally and theoretically. We overcome this challenge superionic AgI by combining THz-frequency Raman polarization-orientation measurements ab-initio molecular computations. Our findings demonstrate clear signatures coupling between mobile ions...

Polar and chiral crystal symmetries confer a variety of potentially useful functionalities upon solids by coupling otherwise noninteracting mechanical, electronic, optical, magnetic degrees freedom. We describe two phases the 3D perovskite, CsSnBr3, which emerge below 85 K due to formation Sn(II) lone pairs their interaction with extant octahedral tilts. Phase II (77 < T K, space group P21/m) exhibits ferroaxial order driven noncollinear pattern pair-driven distortions within plane normal...

The pursuit of structure-property relationships in crystalline metal halide perovskites (MHPs) has yielded an unprecedented combination advantageous characteristics for wide-ranging optoelectronic applications. While MHP structures are readily accessible through diffraction-based structure refinements, providing a clear view associated long-range ordering, the local more recently discovered glassy states remain unexplored. Herein, we utilize Raman spectroscopy, solid-state nuclear magnetic...