The electronic structure and chemical composition of efficient CH3NH3PbI3 perovskite solar cell materials deposited onto mesoporous TiO2 were studied using photoelectron spectroscopy with hard X-rays. With this technique, it is possible to directly measure the occupied energy levels of the perovskite as well as the TiO2 buried beneath and thereby determine the energy level matching of the inter...

Recent studies show that the D'' layer, just above the Earth's core-mantle boundary, is composed of MgSiO3 post-perovskite and has significant lateral inhomogeneity. Here we consider the D'' diversity as related to the single-crystal elasticity of the post-perovskite phase. We measure the single-crystal elasticity of the perovskite Pbnm-CaIrO3 and post-perovskite Cmcm-CaIrO3 using inelastic X-r...

Organic–inorganic hybrid perovskite solar cells (PSCs) are promising third-generation cells. They exhibit high power conversion efficiency (PCE) and, in theory, can be manufactured with less energy than several more established photovoltaic technologies, particularly solution-processed PSCs. Various materials have been widely utilized to modify the buried bottom interface improve performance an...

The preparation of highly efficient perovskite nanocrystal light-emitting diodes is shown. A new trimethylaluminum vapor-based crosslinking method to render the nanocrystal films insoluble is applied. The resulting near-complete nanocrystal film coverage, coupled with the natural confinement of injected charges within the perovskite crystals, facilitates electron-hole capture and give rise to a...

Despite extensive studies on the effects of epitaxial strain on the evolution of the lattice and properties of materials, considerably less work has explored the impact of strain on growth dynamics. In this work, we demonstrate a growth-mode transition from 2D-step flow to self-organized, nanoscale 3D-island formation in PbZr0.2Ti0.8O3/SrRuO3/SrTiO3 (001) heterostructures as the kinetics of the...

Methylammonium lead-iodide (CH3NH3PbI3, hereafter referred to as MAPbI3) perovskite has emerged as a dazzling nova in the solar cell realm. To date, the surface physics of these materials is still puzzling, but in this work, we demonstrate that the optical dynamics in MAPbI3 is primarily determined by the surface states. Pb dangling bonds on the surface of MAPbI3 introduce shallow electronic st...

We review the role that first-principles calculations have played in understanding the effects of substrate-imposed misfit strain on epitaxially grown perovskite ferroelectric films. We do so by analyzing the case of BaTiO3, complementing our previous publications on this subject with unpublished data to help explain in detail how these calculations are done. We also review similar studies in t...

Perovskite materials host an incredible variety of functionalities. Although the lightest element, hydrogen, is rarely encountered in oxide perovskite lattices, it was recently observed as the hydride anion H(-), substituting for the oxide anion in BaTiO3. Here we present a series of 30 new complex hydride perovskite-type materials, based on the non-spherical tetrahydroborate anion BH4(-) and n...

In this paper, we review recent progress and new challenges in the area of oxyfluoride perovskite, especially layered systems including Ruddlesden-Popper (RP), Dion-Jacobson (DJ) and Aurivillius (AV) type perovskite families. It is difficult to synthesize oxyfluoride perovskite using a conventional solid-state reaction because of the high chemical stability of the simple fluoride starting mater...