Meeting the growing global energy demand is one of the important challenges of the 21st century. Currently over 80% of the world's energy requirements are supplied by the combustion of fossil fuels, which promotes global warming and has deleterious effects on our environment. Moreover, fossil fuels are non-renewable energy and will eventually be exhausted due to the high consumption rate. A new type of alternative energy that is clean, renewable and inexpensive is urgently needed. Several candidates are currently available such as hydraulic power, wind force and nuclear power. Solar energy is particularly attractive because it is essentially clean and inexhaustible. A year's worth of sunlight would provide more than 100 times the energy of the world's entire known fossil fuel reserves. Photocatalysis and photovoltaics are two of the most important routes for the utilization of solar energy. However, environmental protection is also critical to realize a sustainable future, and water pollution is a serious problem of current society. Photocatalysis is also an essential route for the degradation of organic dyes in wastewater. A type of compound with the defined structure of perovskite (ABX3) was observed to play important roles in photocatalysis and photovoltaics. These materials can be used as photocatalysts for water splitting reaction for hydrogen production and photo-degradation of organic dyes in wastewater as well as for photoanodes in dye-sensitized solar cells and light absorbers in perovskite-based solar cells for electricity generation. In this review paper, the recent progress of perovskites for applications in these fields is comprehensively summarized. A description of the basic principles of the water splitting reaction, photo-degradation of organic dyes and solar cells as well as the requirements for efficient photocatalysts is first provided. Then, emphasis is placed on the designation and strategies for perovskite catalysts to improve their photocatalytic activity and/or light adsorption capability. Comments on current and future challenges are also provided. The main purpose of this review paper is to provide a current summary of recent progress in perovskite materials for use in these important areas and to provide some useful guidelines for future development in these hot research areas.

Research progress of perovskite materials in photocatalysis- and photovoltaics-related energy conversion and environmental treatment.

Organolead-halide-perovskite-based solar cells have recently received significant attention due to their excellent photovoltaic performance and low cost. The general formula of this perovskite light harvester is RPbX3, where R and X stand for a monovalent organic cation and halide anion, respectively. Structures of the perovskite solar cell are designed based on the function of the perovskite. Organolead halide perovskites can be used either as sensitizers or n- or p-type light harvesters. Rapid progress has been made over the past year since the first report on long-term, durable, 9.7% efficiency perovskite solar cells based on CH3NH3PbI3-sensitized TiO2 in 2012. As a result, power conversion efficiencies as high as 16% have been achieved. Further improvement is expected from this material in terms of understanding charge accumulation and transport properties. Organolead halide perovskite is now regarded as a promising solar cell material, opening new horizons in solar cell research.

Organolead Halide Perovskite: New Horizons in Solar Cell Research

The highly accurate all electrons full potential linearized augmented plane wave method is used to calculate structural, electronic, and optical properties of cubic perovskites CsPbM3 (M=Cl, Br, I). The theoretically calculated lattice constants are found to be in good agreement with the experimentally measured values. It is found that all of these compounds are wide and direct bandgap semiconductors with bandgap located at R-symmetry point, while the bandgap decreases from Cl to I. The electron densities reveal strong ionic bonding between Cs and halides but strong covalent bonding between Pb and halides. Optical properties of these compounds like real and imaginary parts of dielectric functions, refractive indices, extinction coefficients, reflectivities, optical conductivities, and absorption coefficients are also calculated. The direct bandgap nature and high absorption power of these compounds in the visible–ultraviolet energy range imply that these perovskites can be used in optical and optoelectronic devices working in this range of the spectrum.

First principle study of the structural and optoelectronic properties of cubic perovskites CsPbM3 (M=Cl, Br, I)

https://www.repositorio.ufop.br/bitstream/123456789/4861/1/ARTIGO_CommentPredictionLattice.pdf

Comment on “Prediction of lattice constant in cubic perovskites”

Many energy-related materials rely on the uptake and release of large quantities of ions, for example, Li+ in batteries, H+ in hydrogen storage materials, and O2− in solid-oxide fuel cell and related materials. These compositional changes often result in large volumetric dilation of the material, commonly referred to as chemical expansion. This article reviews the current knowledge of chemical expansion and aspires to facilitate and promote future research in this field by providing a taxonomy for its sources, along with recent atomistic insights of its origin, aided by recent computational modeling and an overview of factors impacting chemical expansion. We discuss the implications of chemical expansion for mechanical stability and functionality in the energy applications above, as well as in other oxide-based systems. The use of chemical expansion as a new means to probe other materials properties, as well as its contribution to recently investigated electromechanical coupling, is also highlighted.

J.K. Guo

Papers

Prediction of lattice constant in cubic perovskites