Abstract
[DMA]2ZnCl4, [DMA]2CoCl4 and [DMA]2ZnBr4 crystallized in the monoclinic system, in the P21/n, P21/n and P21/c space groups, respectively. The optical properties of [DMA]2MCl4 (M = Zn and Co) and [DMA]2ZnBr4 were studied using ultraviolet-visible (UV-Vis) spectroscopy in the range of 200–800 nm. The Tauc model was used to determine the band gap energy of each hybrid compound. The calculated values of the direct and indirect band gaps (Egd, Egi) for all samples were found to be in the range of 1.91 eV to 4.29 eV for [DMA]2ZnCl4, 4.76 eV to 5.34 eV for [DMA]2ZnBr4 and 1.77 eV to 3.84 eV for [DMA]2CoCl4. The Urbach energy (Eu), extinction coefficient (k) and refractive index (n) of each compound was calculated. On the other hand, the dispersion of (n) is discussed in terms of the single oscillator Wemple–DiDomenico model. The single oscillator energy (E0), the dispersion energy (Ed), and both the real εr and imaginary parts εi of the dielectric permittivity were estimated. The variation of optical conductivity with the incident photon energy has also been studied. We employed impedance spectroscopy to thoroughly investigate the dipolar dynamics in the prepared materials. The evolution of the dielectric loss, as a function of frequency, showed a distribution of relaxation times, which probably could be of a Maxwell–Wagner type interfacial polarization relaxation, possibly attributed to grain boundary effects or blocking at the contacts. In fact, the current work opens an efficient path to high quality organic–inorganic halide perovskites with good optical properties, which makes them suitable for application in nonlinear optoelectronic devices.
Highlights
[DMA]2ZnCl4, [DMA]2CoCl4 and [DMA]2ZnBr4 crystallized in the monoclinic system, in the P21/n, P21/n and P21/c space groups, respectively
[N(CH3)2H2]2ZnCl4, [N(CH3)2H2]2CoCl4 and [N(CH3)2H2]2ZnBr4 (here in a er [DMA]2MeX4 (Me 1⁄4 Zn and Co and X 1⁄4 Cl and Br)) are members of the A2MeX4 crystal family, which have been extensively studied as typical materials showing various successive phase transitions when the temperature varies
Dimethylammonium tetrachlorozincate [DMA]2ZnCl4, dimethylammonium tetrachlorocolbatate [DMA]2CoCl4 and dimethylammonium tetrabromozincate [DMA]2ZnBr4 crystals have turned out to be very interesting members belonging to an A2MeX4 that undergoes different phase transitions at and below room temperature
Summary
[N(CH3)2H2]2ZnCl4, [N(CH3)2H2]2CoCl4 and [N(CH3)2H2]2ZnBr4 (here in a er [DMA]2MeX4 (Me 1⁄4 Zn and Co and X 1⁄4 Cl and Br)) are members of the A2MeX4 crystal family, which have been extensively studied as typical materials showing various successive phase transitions when the temperature varies. Nonlinear optical crystals, which have high optical band gap, ultrafast response times and low dielectric constant, are in great demand in the optical storage devices, color display units and optical communication systems, etc.[18] compared to organic molecules, organometallic compounds showed strong absorptions in UV/V regions due to metal-toligand and ligand-to-metal charge transfer.[19] On the other hand, all the properties combine to make them as a suitable candidate for multifunctional material development.[20] several studies were performed on [TMA]2MeX4 compounds due to their variety of phase transitions. The white prism-like single crystals of [DMA]2 ZnBr4 were collected, washed with a small amount of distilled water, and dried in open air
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