Highly Stable, New, Organic-Inorganic Perovskite (CH3 NH3 )2 PdBr4 : Synthesis, Structure, and Physical Properties.

Lead halide perovskites have attracted striking attention recently, due to their appealing properties. However, toxicity and stability are two main factors restricting their application. In this work, a less toxic and highly stable Pd-based hybrid perovskite was experimentally synthesized, after exploring different experimental conditions. This new hybrid organic-inorganic perovskite (CH3 NH3 )2 PdBr4 was found to be an orthorhombic crystal (Cmce, Z=4) with lattice parameters a=8.00, b=7.99, c=18.89 Å. The Cmce symmetry and lattice parameters were confirmed using Pawley refinement and the atoms positions were confirmed based on DFT calculation. This perovskite compound was determined to be a p-type semiconductor, with a resistivity of 102.9 kΩ cm, a carrier concentration of 3.4 ×1012 cm-3 , and a mobility of 23.4 cm2 (V s)-1 . Interestingly, XRD and UV/Vis measurements indicated that the phase of this new perovskite was maintained with an optical gap of 1.91 eV after leaving in air with a high humidity of 60 % for 4 days, and unchanged for months in N2 atmosphere; much more stable than most existing organic-inorganic perovskites. The synthesis and various characterizations of this work further the understanding of this (CH3 NH3 )2 PdBr4 organic-inorganic hybrid perovskite material.

Light enhanced energy storage ability through a hybrid plasmonic Ag nanowire decorated hydroxide "skin structure".

By decorating nickel copper hydroxide (NCH) with Ag nanowires (Ag NWs), a 1.7 fold enhancement in areal capacitance (5.4 F cm-2) and a 1.8 fold increment in gravimetric capacitance (3182 F g-1) under light illumination were achieved. The improved supercapacitor performances of the composites under visible-light illumination were demonstrated and a reasonable explanation for this newly-discovered phenomenon was proposed. The plasmonic effect of Ag NWs was demonstrated by hot-electron generation. The decorated Ag NWs served as a stimulus for redox reactions. This research provides a tantalizing opportunity for enhancing the supercapacitor performance by exploiting surface plasmon metals. The finding from this study will be informative for the future design of supercapacitor electrodes.

Remarkable improvement in supercapacitor performance by sulfur introduction during a one-step synthesis of nickel hydroxide.

Composition control by introducing sulfur during a one-step synthesis of nickel hydroxide is successfully achieved using our unique design. And it has been demonstrated to be an effective strategy by increasing the specific capacitance by more than 40%. A systematic study reveals that as the sulfur (S) to oxygen (O) ratio is increased, the specific capacitance first increases and then decreases. At a S to O ratio of approximately one, the composite outperforms other ratios, delivering a remarkable capacitance of 2801 F g-1 at 2 A g-1. More importantly from the customer point of view and viability for practical applications, a high specific capacitance of 457 F g-1 is achieved per total weight of the active material plus substrate. The energy density per weight of the active materials reaches a high value of 61 Wh kg-1. The energy density per total weight of the active material and substrate reached a very high value of 34 Wh kg-1. A detailed study on the role of S is performed experimentally and theoretically. The results reveal for the first time that sulfur itself does not contribute to the increase in specific performance, and the significant improvements in capacitance and energy density can be attributed to sulfur induced refinement in clusters and morphology.

Influence of Ligands on the Formation of Kesterite Thin Films for Solar Cells: A Comparative Study.

The preparation of solar-cell-grade Cu2 ZnSnS4 (CZTS) thin films from ligand-capped small-grained CZTS particles remains hindered by problems of phase segregation, composition non-uniformity, and in particular carbon-layer formation. Herein, through a systematic comparative study of annealed films of CZTS nanocrystals prepared using conventional oleylamine and those prepared using formamide, these problems are found to be mainly attributable to the influence of the ligands, and mechanisms are proposed. Importantly, the origin of the carbon layer in oleylamine-capped CZTS films is revealed to be the reaction between oleylamine and sulfur. This carbon layer has a very poor electrical conductivity, which can be the reason for the limited performance of such films. Fortunately, these problems can almost all be avoided by replacing oleylamine with formamide to form CZTS films.

(CH3 NH3 )2 PdCl4 : A Compound with Two-Dimensional Organic-Inorganic Layered Perovskite Structure.

The synthesis of previously unknown perovskite (CH3 NH3 )2 PdCl4 is reported. Despite using an organic cation with the smallest possible alkyl group, a 2D organic-inorganic layered Pd-based perovskites was still formed. This demonstrates that Pd-based 2D perovskites can be obtained even if the size of the organic cation is below the size limit predicted by the Goldschmidt tolerance-factor formula. The (CH3 NH3 )2 PdCl4 phase has a bulk resistivity of 1.4â€…Ω cm, a direct optical gap of 2.22 eV, and an absorption coefficient on the order of 104  cm-1 . XRD measurements suggest that the compound is moderately stable in air, an important advantage over several existing organic-inorganic perovskites that are prone to phase degradation problems when exposed to the atmosphere. Given the recent interest in organic-inorganic perovskites, the synthesis of this new Pd-based organic-inorganic perovskite may be helpful in the preparation and understanding of other organic-inorganic perovskites.