相关论文: Anharmonic stabilization and band gap renormalizat…
CsSnI3 is a promising eco-friendly solution for energy harvesting technologies. It exists at room temperature in either a black perovskite polymorph or a yellow 1D double-chain, which irreversibly deteriorates in the air. In this work, we…
Metal halide perovskites exhibit a fairly linear increase of the bandgap with increasing temperature, when crystallized in a tetragonal or cubic phase. In general, both thermal expansion and electron-phonon interaction effects contribute…
Anharmonic atomic motions can strongly influence the optoelectronic properties of materials but how these effects are connected to the underlying phonon band structure is not understood well. We investigate how the electronic band gap is…
We investigate the influence of three- and four-phonon scattering, perturbative anharmonic phonon renormalization, and off-diagonal terms of coherent phonons on the thermal conductivity of CsPbBr3 phase change perovskite, by using advanced…
The ability to finely tune optoelectronic properties in semiconductors is crucial for the development of advanced technologies, ranging from photodetectors to photovoltaics. In this work, we propose a novel strategy to achieve such…
Halide perovskite (HP) semiconductors exhibit unique strong coupling between the electronic and structural dynamics. The high-temperature cubic phase of HPs is known to be entropically stabilized, with imaginary frequencies in the…
We determine the impact of anharmonic thermal vibrations on the fundamental band gap of CsPbBr$_3$, a prototypical model system for the broader class of halide perovskite semiconductors. Through first-principles molecular dynamics and…
The work carried out first-principles calculations within the framework of density functional theory to study the structural stability of the CsSnI3 compound and the influence of phase transitions on their electronic and optical properties.…
The local crystal structures of many perovskite-structured materials deviate from the average space group symmetry. We demonstrate, from lattice-dynamics calculations based on quantum chemical force constants, that all the caesium-lead and…
Chalcogenide perovskites have emerged as promising lead free materials for photovoltaic and thermoelectric applications. Among them, BaZrS3 has attracted particular attention due to its thermal and chemical stability, favorable…
Lead halide perovskites are causing a change of paradigm in photovoltaics. Among other peculiarities, these perovskites exhibit an atypical temperature dependence of the fundamental optical gap: It decreases in energy with decreasing…
The structural, electronic, optical and elastic properties of perovskites of the $\alpha$-, $\beta$- and $\gamma$-phase family CsSnI$_{3-x}$Cl$_x$ (x = 0, 1, 2, 3) are analyzed by ab initio methods using GGA, SCAN and HSE06. It is found…
Environmental effects and intrinsic energy-loss processes lead to fluctuations in the operational temperature of solar cells, which can profoundly influence their power conversion efficiency. Here we determine from first principles the…
We develop a first-principles approach for the treatment of vibronic interactions in solids that overcomes the main limitations of state-of-the-art electron-phonon coupling formalisms. In particular, anharmonic effects in the nuclear…
We use solid-state methods to synthesize single crystals of perovskite-phase cesium lead iodide (${\gamma}$-CsPbI3) that are kinetically stable at room temperature. Single crystal X-ray diffraction characterization shows that the compound…
Cs$_2$KInI$_6$ is a promising lead-free halide double perovskite with a calculated direct band gap of 1.24 eV, ideal for solar cell applications. Our first-principles calculations reveal that its cubic phase (Fm$\bar{3}$m) is dynamically…
Anharmonicity and local disorder (polymorphism) are ubiquitous in perovskite physics, inducing various phenomena observed in scattering and spectroscopy experiments. Several of these phenomena still lack interpretation from first-principles…
The halide double perovskite Cs$_2$AgBiBr$_6$ has been proposed as a potential replacement for organic halide perovskites for photovoltaic applications. Further investigation of its dielectric response, optical properties and structural…
The phonon spectrum of the high-pressure simple cubic phase of calcium, in the harmonic approx- imation, shows imaginary branches that make it mechanically unstable. In this letter, the phonon spectrum is recalculated using…
We have carried out temperature-dependent x-ray diffraction and Raman scattering experiments on powder $Cs_3Bi_2Br_9$. Trigonal to monoclinic structural transition at around 95 K is discussed and shown to be driven by the softening of the…