The high pressure structures, metallization, and superconductivity of recently synthesized H2-containing compounds (H2S)2H2 are elucidated by ab initio calculations. The ordered crystal structure with P1 symmetry is determined, supported by the good agreement between theoretical and experimental X-ray diffraction data, equation of states, and Raman spectra. The Cccm structure is favorable with partial hydrogen bond symmetrization above 37 GPa. Upon further compression, H2 molecules disappear and two intriguing metallic structures with R3m and Im-3m symmetries are reconstructive above 111 and 180 GPa, respectively. The predicted metallization pressure is 111 GPa, which is approximately one-third of the currently suggested metallization pressure of bulk molecular hydrogen. Application of the Allen-Dynes-modified McMillan equation for the Im-3m structure yields high Tc values of 191 K to 204 K at 200 GPa, which is among the highest values reported for H2-rich van der Waals compounds and MH3 type hydride thus far.

All inorganic perovskite nanocrystals (NCs) of CsPbX (X = Cl, Br, I, or their mixture) are regarded as promising candidates for high-performance light-emitting diode (LED) owing to their high photoluminescence (PL) quantum yield (QY) and easy synthetic process. However, CsPbX NCs synthesized by the existing methods, where oleic acid (OA) and oleylamine (OLA) are generally used as surface-chelating ligands, suffer from poor stability due to the ligand loss, which drastically deteriorates their PL QY, as well as dispersibility in solvents. Herein, the OA/OLA ligands are replaced with octylphosphonic acid (OPA), which dramatically enhances the CsPbX stability. Owing to a strong interaction between OPA and lead atoms, the OPA-capped CsPbX (OPA-CsPbX) NCs not only preserve their high PL QY (>90%) but also achieve a high-quality dispersion in solvents after multiple purification processes. Moreover, the organic residue in purified OPA-CsPbBr is only ∼4.6%, which is much lower than ∼29.7% in OA/OLA-CsPbBr. Thereby, a uniform and compact OPA-CsPbBr film is obtained for LED application. A green LED with a current efficiency of 18.13 cd A, corresponding to an external quantum efficiency of 6.5%, is obtained. Our research provides a path to prepare high-quality perovskite NCs for high-performance optoelectronic devices.

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We demonstrated compact SnO2thin films prepared by sinter-less spin-coating processes as an electron selective contact for CH3NH3PbI3-based planar-heterojunction perovskite solar cells (PSCs).