Hybrid CPbX 3 (C:C s, CH 3 NH 3 ;X :B r, I) perovskites possess excellent photovoltaic properties but are highly toxic, which hinders their practical application. Unfortunately,a ll Pb-free alternatives based on Sn and Ge are extremely unstable. Although stable and non-toxic C 2 ABX 6 double perovskites based on alternating corner-shared AX 6 and BX 6 octahedra (A = Ag, Cu;B = Bi, Sb) are possible, they have indirect and wide band gaps of over 2eV. However,i si tn ecessary to keep the corner-shared perovskite structure to retain good photovoltaic properties? Here, we demonstrate another family of photovoltaic halides based on edge-shared AX 6 and BX 6 octahedra with the general formula A a B b X x (x = a + 3 b)s uch as Ag 3 BiI 6 ,A g 2 BiI 5 ,A gBiI 4 , AgBi 2 I 7 .A sp erovskites were named after their prototype oxide CaTiO 3 discovered by Lev Perovski, we propose to name these new ABX halidesa sr udorffitesa fter Walter Rüdorff,w ho discoveredt heir prototype oxide NaVO 2 .W es tudied structural and optoelectronic properties of severalh ighly stable and promising Ag-Bi-I photovoltaic rudorffites that feature direct band gaps in the range of 1.79- Photovoltaic (PV) hybrid lead halide perovskites were first reported by Kojimae tal. [1] in 2006 with power conversion efficiency (PCE) of 2.2 %i nadye-sensitized solarc ell (DSSC) device configuration. However,t hese materials gained considerable attention only 6years later after two incremental improvements of their PCE to 3.8 %b yK ojimae tal. [2] and to 6.2 %b yI me tal. [3] Substitution of the liquid electrolyte with an efficient polymer hole-extraction layer by Lee et al. [4] in 2012 increased PCE to 10.9 %and was the turning point in perovskite photovoltaics that openedaway towardh ighly efficient and stable perovskite PV devices.S ince 2012 many researchers, mainly from the dye-sensitized and organic PV fields, joined the exciting research on perovskite solar cells. As ar esult, the PCE of the perovskite solarc ells showed as teep sigmoidal growth thatl ed to the contemporary efficiency of over 22 %. [5] Although this PCE is on par with other highly efficient thin-film PV technologies based on cadmium telluride (CdTe) and copper-indium-gallium selenide (CIGS), lead halide perovskites have the significant advantage of being solution processable, whicho fferss ubstantial cost reduction. Unfortunately,t he relianceo nh ighly toxic Pb hinders the commercial potentialo ft his technology. The toxicity of Pb is very high. The 50 %l ethal dose of lead [LD 50 (Pb)] is less than 5mgp er kg of body weight. In contrast to CdTe, which has excellent stability and negligible solubility in water with as olubility constant of K SP = 10 À34 ,P b-based halide perovskites can easily degrade and Pb can escape from ab roken PV module owing to the moderate solubility of PbI 2 (K SP = 4.4 10 À9 ). Despite various attempts to quantify the impact of potential pollution andi ntroduce life-cycle business modelst hat include integrity monitoring and recycling of perovskite PV modules, ...
A saturated aqueous solution of sodium perchlorate (SSPAS) was found to be electrochemically superior, because the potential window is remarkably wide to be approximately 3.2 V in terms of a cyclic voltammetry. Such a wide potential window has never been reported in any aqueous solutions, and this finding would be of historical significance for aqueous electrolyte to overcome its weak point that the potential window is narrow. In proof of this fact, the capability of SSPAS was examined for the electrolyte of capacitors. Galvanostatic charge-discharge measurements showed that a graphite-based capacitor containing SSPAS as an electrolyte was stable within 5% deviation for the 10,000 times repetition at the operating voltage of 3.2 V without generating any gas. The SSPAS worked also as a functional electrolyte in the presence of an activated carbon and metal oxides in order to increase an energy density. Indeed, in an asymmetric capacitor containing MnO2 and Fe3O4 mixtures in the positive and negative electrodes, respectively, the energy density enlarged to be 36.3 Whkg−1, which belongs to the largest value in capacitors. Similar electrochemical behaviour was also confirmed in saturated aqueous solutions of other alkali and alkaline earth metal perchlorate salts.
Nearly complete gasification of organic compounds has been achieved by stoichiometrically insufficient amounts of RuO2 in supercritical water (SCW) to provide CH4, CO2 and H2, all the hydrogen atoms of which originate from water, and the catalytic effect of RuO2 results from a redox couple of Ru(IV)/Ru(II) induced by SCW.
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