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Mixed metal halide perovskites are gaining paramount interest due to efficient band gap tenability and improved optical properties compared to their single metal halide perovskites. It is thus valuable to investigate compositional changes in lead halide perovskites to explore energy changes. Herein, we report the synthesis of a lead to lead free hybrid perovskite solid solution (CH3NH3Pb1−xCuxBr3) as nanoparticles and films. The increasing concentration of Cu2+ ions in the site of the Pb2+ ion in the perovskite shifted the diffraction peaks to a larger angle. Uniform spherically shaped nanoparticles were synthesized by a wet chemical method, the higher Cu2+ concentration leads to agglomeration, producing sheet like morphologies. However, the deposition of thin films of CH3NH3Pb1−xCuxBr3 perovskite solid solution shows that well defined morphologies begin to appear with increasing concentrations of Cu2+ in the perovskite structure. The as-prepared bulk lead free CH3NH3CuBr3 perovskite shows a band gap of 1.65 eV. A blue shift in photoluminescence (PL) was observed with copper enriched hybrid perovskites. [ABSTRACT FROM AUTHOR]

Species with a lower ionization energy than alkali atoms are referred to as superalkalis. Typical superalkalis include a central electronegative core with excess metal ligands. We propose a new series of “non-metallic” NnH3n+1+ superalkali cations based on the results of the MP2/6-311++G(d,p) computations. These cations are designed by successive replacement of H-ligands of ammonium cations (NH4+) by ammonium (NH4) moieties. The resulting NnH3n+1+ cations, which can be expressed in the form of [NH4…(n− 1)NH3]+ complexes, possess a number of unusual N–H…N type of partially covalent H-bonds, with the interaction energy in the range of 7.8–24.3 kcal mol−1. These cations are stable against loss of a proton (NnH3n + H+) and loss of ammonia [(n− 1)NH3 + NH4+]. The vertical electron attachment energies (EAvs) of NnH3n+1+ decrease monotonically from 4.39 eV for n = 1 to 2.39 eV for n = 5, which suggests their superalkali nature. This can be explained on the basis of electron localization on the core (central) N-atom (Qc), as the EAv correlates linearly with Qc. We have also demonstrated that this series may be continued to obtain new superalkali cations with even lower EAv, by exemplifying N9H28+ with an EAv of 1.84 eV. N9H28+ is stabilized by four partially covalent H-bonds (8.5 kcal mol−1 each) and four electrostatic H-bonds (0.4 kcal mol−1 each). This led to an exponential relation between EAv and n, which may provide an approximate EAv for any value of n in the NnH3n+1+ series. [ABSTRACT FROM AUTHOR]

Photoinduced electron transfer (PET) with the formation of stable radicals plays an important role in many areas. In this work, PET and color change of two sulfone-based donor–acceptor molecules were observed for the first time in the solid state. Generation of radicals was confirmed by experimental and theoretical data. The radicals could be stable in the air and at high temperature (e.g. 105 °C) in the solid state. Introducing an electron-donating substituent (such as –NH2) increases the molecular dipole moment and promotes the PET process. Sulfone-based molecules observed in this work and their analogs may be applied in several potential applications such as photoswitching, photochromism, energy conversion, and photocatalysis. [ABSTRACT FROM AUTHOR]

Herein, we synthesized CH3NH3PbBr3 nanoparticles using succinic acid and oleylamine at a fixed ratio as ligands. The formed stable CH3NH3PbBr3 NCs exhibit narrow green photoluminescence with high quantum yield as compared to the perovskites formed through oleic acid. Moreover, a fluorescent keypad lock security device authorizing password entries was constructed based on the output emission signal. The fluorescent keypad lock could be unlocked upon entering the correct sequence of password, i.e. MPDSOC. Furthermore, characterizations and morphology studies have been performed using UV, PL, XRD, TCSPC and TEM. In addition, stability tests were monitored using fluorescence spectra. [ABSTRACT FROM AUTHOR]