Unraveling the Chemical Nature of the 3D "Hollow" Hybrid Halide Perovskites.

The newly introduced class of 3D halide perovskites, termed "hollow" perovskites, has been recently demonstrated as light absorbing semiconductor materials for fabricating lead-free perovskite solar cells with enhanced efficiency and superior stability. Hollow perovskites derive from three-dimensional (3D) AMX perovskites ( A = methylammonium (MA), formamidinium (FA); M = Sn, Pb; X = Cl, Br, I), where small molecules such as ethylenediammonium cations ( en) can be incorporated as the dication without altering the structure dimensionality. We present in this work the inherent structural properties of the hollow perovskites and expand this class of materials to the Pb-based analogues.

CuISe: A Metal-Inorganic Framework Wide-Bandgap Semiconductor for Photon Detection at Room Temperature.

CuISe is a new wide-bandgap semiconductor with high stability and great potential toward hard radiation and photon detection. CuISe crystallizes in the rhombohedral R3̅m space group with a density of d = 5.287 g·cm and a wide bandgap E of 1.

Enhanced photovoltaic performance and stability with a new type of hollow 3D perovskite {en}FASnI.

Perovskite solar cells have revolutionized the fabrication of solution-processable solar cells. The presence of lead in the devices makes this technology less attractive, and alternative metals in perovskites are being researched as suitable alternatives. We demonstrate a new type of tin-based perovskite absorber that incorporates both ethylenediammonium (en) and formamidinium (FA), forming new materials of the type {en}FASnI.

Defect Antiperovskite Compounds HgQI (Q = S, Se, and Te) for Room-Temperature Hard Radiation Detection.

The high Z chalcohalides HgQI (Q = S, Se, and Te) can be regarded as of antiperovskite structure with ordered vacancies and are demonstrated to be very promising candidates for X- and γ-ray semiconductor detectors. Depending on Q, the ordering of the Hg vacancies in these defect antiperovskites varies and yields a rich family of distinct crystal structures ranging from zero-dimensional to three-dimensional, with a dramatic effect on the properties of each compound. All three HgQI compounds show very suitable optical, electrical, and good mechanical properties required for radiation detection at room temperature.

The Two-Dimensional ACdBiQ (A = K, Rb, Cs; Q = S, Se): Direct Bandgap Semiconductors and Ion-Exchange Materials.

We report the new layered chalcogenides ACdBiQ (A = Cs, Rb, K; Q = S and A = Cs; Q = Se). All compounds are isostructural crystallizing in the orthorhombic space group Cmcm, with a = 4.0216(8) Å, b = 6.

Structural, electronic, and linear optical properties of organic photovoltaic PBTTT-C14 crystal.

Poly(2,5-bis(3-tetradecylthiophen-2yl)thieno(3,2-b)thiophene) (PBTTT-C14) is an important electro-optical polymer, whose three-dimensional crystal structure is somewhat ambiguous and the fundamental electronic and linear optical properties are not well known. We carried out first-principles calculations to model the crystal structure and to study the effect of side-chains on the physical structure and electronic properties. Our calculations suggest that the patterns of side-chain has little direct effect on the valence band maximum and conduction band minimum but they do have impact on the bandgap through changing the π-π stacking distance.