Compared to the Ruddlesden–Popper-phase, we find that the Dion–Jacobson-phase 2D iodide perovskites have a slower rate of non-radiative carrier recombination.

Hybrid halide perovskites frequently undergo structural expansion due to various stimuli, significantly affecting their electronic properties and in particular their charge carrier dynamics. It is essential to atomistically model how geometric changes modify electronic characteristics that are important for applications such as light harvesting and lighting. Using ab initio simulations, here we investigate the structural dynamics and optoelectronic properties of FAPbI3 under tensile strain. The applied strain leads to elongation of the Pb–I bonds and a decrease in the level of PbI6 octahedral tilting, which manifests as blue-shifts in band gaps. Nonadiabatic molecular dynamics simulations further reveal that charge carrier recombination rates moderately decrease in these expanded lattices. The complex influence of lattice dynamics on electron–phonon scattering results in a longer carrier lifetime, which is advantageous for efficient solar cells. By providing detailed information about the structure–property relationships, this work emphasizes the role of controlled lattice expansion in enhancing the electronic functionalities of hybrid perovskites.

Optoelectronic devices based on all-inorganic perovskite systems are an energy-efficient source of lighting due to their high photoluminescence quantum yield (QY). However, dominant surface trapping continues to plague the field, despite their high defect tolerance, as evidenced by the several-fold improvements in the external quantum efficiency of perovskite nanocrystals (NCs) upon appropriate surface passivation or physical confinement between high-band-gap materials. Here, we introduce the concept of drip-feeding of photoexcited electrons from an impurity-induced spin-forbidden state to address this major shortcoming. An increased and delayed (about several milliseconds) excitonic QY, Raman spectroscopy demonstrating specific vibrational modes of the PbX6 octahedra, and density functional theory establish the electron back-transfer, signifying an efficient recombination. We term this electron back-transfer from Mn2+ to the host conduction band in this prototypical example of Mn-doped CsPbX3 (X = Cl, Br) NCs through vibrational coupling as vibrationally assisted delayed fluorescence (VADF).

Metal halide perovskites have recently emerged as one of the most promising classes of semiconductors for various applications, especially in the field of optoelectronics. Lead-based halide perovskite materials, virtually unexploited for decades, have become prominent candidates due to their unique and intrinsic physicochemical and optical properties. Current challenges faced by the scientific community to capitalize on the properties of Pb-based perovskites are mainly associated with environmental concerns due to the toxicity of Pb and their poor stability. Under this context, over recent years, a number of new Pb-free halide perovskite (and perovskite-like) semiconductor classes have been introduced. This Perspective reviews recent developments in Pb-free halide perovskites, which specifically target their application in solar cells, light-emitting devices, and photocatalysts. Each type of Pb-free material is paired with a specific optoelectronic application, and the latest record performances are reported. Although these materials do not yet exhibit as attractive intrinsic optoelectronic properties as the Pb-based halide perovskites, their potential as alternatives for well-suited applications is discussed.

We have performed density functional theory calculations to study the adsorption of methanol on graphene−BN lateral heterostructures and highly intermixed BCN, as well as on pure graphene and pure h-BN. We find that the adsorption energy is enhanced significantly on the heterostructures, obtaining the largest enhancement on a triangular graphene island embedded in a h-BN matrix with zigzag interfaces. We find that while the majority of the binding arises from London dispersion interactions, this enhancement is largely due to Keesom interactions, i.e., due to electrostatic interactions between the permanent electric dipole moment of the methanol molecule and permanent charges on the heterostructured substrates. These charges arise due to polar discontinuities at certain kinds of C−BN interfaces. We find a strong correlation between the adsorption energy and these interface charges. These results provide insight into experimental findings that methanol binds more strongly to BN-doped carbon foams than to plain carbon foam. Our findings suggest design principles for engineering materials for use in cooling devices that can be used to convert waste heat or solar energy into useful work, using thermal energy storage.

A simple chemical reduction approach to doping β-FeSi2 with boron and its comprehensive characterization through experimental and density functional theorem (DFT) Analyses.

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