Disentangling the effects of structure and lone-pair electrons in the lattice dynamics of halide perovskites.

Halide perovskites show great optoelectronic performance, but their favorable properties are paired with unusually strong anharmonicity. It was proposed that this combination derives from the ns electron configuration of octahedral cations and associated pseudo-Jahn-Teller effect. We show that such cations are not a prerequisite for the strong anharmonicity and low-energy lattice dynamics encountered in these materials.

Alloying Effects on Charge-Carrier Transport in Silver-Bismuth Double Perovskites.

Alloying is widely adopted for tuning the properties of emergent semiconductors for optoelectronic and photovoltaic applications. So far, alloying strategies have primarily focused on engineering bandgaps rather than optimizing charge-carrier transport. Here, we demonstrate that alloying may severely limit charge-carrier transport in the presence of localized charge carriers (e.

Optically Induced Long-Lived Chirality Memory in the Color-Tunable Chiral Lead-Free Semiconductor ()/()-CHEABiBrI ( = 0-10).

Hybrid organic-inorganic networks that incorporate chiral molecules have attracted great attention due to their potential in semiconductor lighting applications and optical communication. Here, we introduce a chiral organic molecule ()/()-1-cyclohexylethylamine (CHEA) into bismuth-based lead-free structures with an edge-sharing octahedral motif, to synthesize chiral lead-free ()/()-CHEABiBrI crystals and thin films. Using single-crystal X-ray diffraction measurements and density functional theory calculations, we identify crystal and electronic band structures.

Probing the Disorder Inside the Cubic Unit Cell of Halide Perovskites from First-Principles.

Strong deviations in the finite temperature atomic structure of halide perovskites from their average geometry can have profound impacts on optoelectronic and other device-relevant properties. Detailed mechanistic understandings of these structural fluctuations and their consequences remain, however, limited by the experimental and theoretical challenges involved in characterizing strongly anharmonic vibrational characteristics and their impact on other properties. We overcome some of these challenges by a theoretical characterization of the vibrational interactions that occur among the atoms in the prototypical cubic CsPbBr.

Transversal Halide Motion Intensifies Band-To-Band Transitions in Halide Perovskites.

Despite their puzzling vibrational characteristics that include strong signatures of anharmonicity and thermal disorder already around room temperature, halide perovskites (HaPs) exhibit favorable optoelectronic properties for applications in photovoltaics and beyond. Whether these vibrational properties are advantageous or detrimental to their optoelectronic properties remains, however, an important open question. Here, this issue is addressed by investigation of the finite-temperature optoelectronic properties in the prototypical cubic CsPbBr , using first-principles molecular dynamics based on density-functional theory.

Mixtures of Dopant-Free Spiro-OMeTAD and Water-Free PEDOT as a Passivating Hole Contact in Perovskite Solar Cells.

Doped spiro-OMeTAD at present is the most commonly used hole transport material (HTM) in n-i-p-type perovskite solar cells, enabling high efficiencies around 22%. However, the required dopants were shown to induce nonradiative recombination of charge carriers and foster degradation of the solar cell. Here, in a novel approach, highly conductive and inexpensive water-free poly(3,4-ethylenedioxythiophene) (PEDOT) is used to replace these dopants.