It is shown that 21 ABX(3) perovskites with tilted BX(6) octahedra and layered ordering of A cations can be generated on the basis of group-subgroup relations. These structures (with 16 different space groups) are classified into ten diffraction types in terms of the conditions for superstructure reflections caused by the ordering of A cations, tilting of BX(6) octahedra and structural absences...

We report valence and conduction band densities of states measured via ultraviolet and inverse photoemission spectroscopies on three metal halide perovskites, specifically methylammonium lead iodide and bromide and cesium lead bromide (MAPbI3, MAPbBr3, CsPbBr3), grown at two different institutions on different substrates. These are compared with theoretical densities of states (DOS) calculated ...

The organic-inorganic hybrid lead trihalide perovskites have been emerging as the most attractive photovoltaic materials. As regulated by Shockley-Queisser theory, a formidable materials science challenge for improvement to the next level requires further band-gap narrowing for broader absorption in solar spectrum, while retaining or even synergistically prolonging the carrier lifetime, a criti...

Metals with large positive magnetoresistance are rare. We demonstrate that antiferromagnetic metallic states, as have been predicted for the double perovskites, are excellent candidates for huge positive magnetoresistance. An applied field suppresses long range antiferromagnetic order leading to a state with short range antiferromagnetic correlations and strong electronic scattering. The field ...

Ferroelectric solar cells based on ferroelectric oxides have attracted significant attention owing to many unique advantages, such as the switchable photocurrent and photovoltage, and the above bandgap open circuit voltages. However, the small photocurrent densities of the typical ferroelectric solar cells greatly limit their photovoltaic performance. In this report, we experimentally revealed ...

Organometal lead halide perovskites have been widely used as the light harvester for high-performance solar cells. However, typical perovskites of methylammonium lead halides (CH3NH3PbX3, X=Cl, Br, I) are usually sensitive to moisture in ambient air, and thus require an inert atmosphere to process. Here we demonstrate a moisture-induced transformation of perovskite crystals in a triple-layer sc...

We formulate a concise deformation theory for periodic bar-and-joint frameworks in Rd and illustrate our algebraic–geometric approach on frameworks related to various crystalline structures. Particular attention is given to periodic frameworks modelled on silica, zeolites and perovskites. For frameworks akin to tectosilicates, which are made of one-skeleta of d-dimensional simplices, with each ...

Lead halide perovskites have been demonstrated as high performance materials in solar cells and light-emitting devices. These materials are characterized by coherent band transport expected from crystalline semiconductors, but dielectric responses and phonon dynamics typical of liquids. This "crystal-liquid" duality implies that lead halide perovskites belong to phonon glass electron crystals, ...

The Perdew-Burke-Ernzerhof generalized gradient approximation to the density functional theory is tested with respect to sensitivity to the choice of the value of the parameter κ, which is associated to the degree of localization of the exchange-correlation hole. A study of structural and dynamical properties of four selected ferroelectric perovskites is presented. The originally proposed value...

The development of active, cost-effective and stable oxygen-evolving catalysts is one of the major challenges for solar-to-fuel conversion towards sustainable energy generation. Iridium oxide exhibits the best available compromise between catalytic activity and stability in acid media, but it is prohibitively expensive for large-scale applications. Therefore, preparing oxygen-evolving catalysts...