Here we report to tunability of palladium-based vacancy ordered halide perovskites that can undergo anion-exchange to create core–shell heterostructures. These structures were employed as photoanodes for photoelectrochemical solar water splitting.
Abstract Formamidine lead iodide perovskite (FAPbI3) is often used as a light-absorbing layer in solar cells to alleviate the energy crisis because of its good photovoltaic properties. However, its lack of stability is also an obstacle to the current development. It has been found that doping with different kinds of elements at different sites can enhance its stability and improve the photoelectric conversion efficiency of solar cells. In this study, the geometry, electronic structure, and optical properties of FA1−xCsxPbI3−yCly were calculated using Cs and Cl co-doped with FAPbI3 using first principles. The analysis revealed that the Goldschmidt factors of the doped system were between 0.962 and 0.974, indicating that the systems could maintain a stable perovskite structure and that the doped system had lower energy and a more stable structure. By calculating the energy bands, it was found that the doped ions have a more pronounced effect on the increase in the dispersion at the bottom of the conduction band than on the decrease in the dispersion at the top of the valence band of the system, and the reduction of the effective mass of carriers is more favorable for transport. As for the optical properties, the right amount of doping is favorable for the improvement of light absorption, whereas excess doping shortens the light absorption range and weakens the light absorption effect, in which FA0.875Cs0.125PbI2.958Cl0.125 has the largest light absorption coefficient. It is shown that the photoelectric properties of FAPbI3 can be effectively modulated by the co-doping with Cs and Cl, which can provide a theoretical reference for the precise preparation of more efficient solar cells.
Zeina Assi, Alexander Gareth Schneider, Anna Christina Ulpe
et al.
The B–H bond length of the borohydride anion (BH4−) in alkali metal borohydrides MBH4 with M = Na, K, Rb, Cs, and diluted in different alkali halide matrices, was investigated experimentally by infrared spectroscopy (FTIR) and theoretically using first principles calculations. The peak positions in IR absorption spectra of NaBH4 pressed at 754 MPa in halides NaX and KX with X = Cl, Br, I show significant variations indicating ion exchange effects between the halide and NaBH4. For NaBH4 in NaBr, NaI, KBr and KI pellets, the peak positions indicate that BH4− could be highly diluted in the AX matrix, which renders an isolation of BH4− in AX (i-BH4−). For NaBH4 in NaCl and KCl pellets, a solution of BH4− in AX occurred only after a further thermal treatment up to 450 °C. The observed peak positions are discussed with respect to the lattice parameter (a0), anion to cation ratio (R = rA/rX), standard enthalpy of formation (ΔfH) and ionic character (Ic) of the halides. A linear relation is obtained between ν3(i-BH4−) and the short-range lattice energies of AX. Density functional theory (DFT) calculations at generalized gradient approximation (GGA) level were used to calculate the IR vibrational frequencies ν4, ν3 and ν2 + ν4 for series of compositions Na(BH4)0.25X0.75 with X = Cl, Br, I, and MBH4. The theoretical and experimental results show the same trends, indicating the rigidity of the B–H bond length and the failure of Badger’s rule.
Correction for ‘Initiation and future prospects of colloidal metal halide double-perovskite nanocrystals: Cs 2 AgBiX 6 (X = Cl, Br, I)’ by Vikash Kumar Ravi et al. , J. Mater. Chem. A , 2018, DOI: 10.1039/c8ta06126b.
AbstractThe title compounds are prepared by solid state reaction of appropriate amounts of Zr, ZrCl4, ZrI4, CsCl, and elemental boron (Ta containers, 800 °C, 5 weeks).
AbstractThe new title compound is synthesized from stoichiometric amounts of CsCl and HgI2 dissolved in acetone (45 °C, 24 h) and characterized by single crystal XRD, IR, Raman, UV/VIS diffuse reflectance spectroscopy, and nonlinear optical property measurements.
Objective: To examine trends in preterm births, especially those less than 33 weeks gestation, occurring in perinatal centres in New South Wales (NSW) from 1992 to 2001.Methods: Population data were obtained from the NSW Midwives’ Data Collection. Trends in the proportion of births in perinatal centres by gestation and by type of preterm birth (spontaneous or elective), and in Apgar scores and neonatal mortality were determined.Results: The preterm birth rate increased from 6.1% in 1992 to 6.7% in 2001. Factors contributing to the increase in preterm births were multiple births and elective preterm deliveries. Births less than 33 weeks gestation in perinatal centres increased from 76% to 83% and for multiple births from 77% to 87%. This coincided with a decrease in 1‐minute Apgar scores less than 4 but no significant change in 5‐minute Apgar scores or neonatal mortality.Conclusions: Progress has been made towards the National Health and Medical Research Council guideline that births less than 33 weeks gestation occur in perinatal centres. Preterm births are increasing, creating greater demands for neonatal intensive care unit care and ventilation services.