Microfluidic Approach for Lead Halide Perovskite Flexible Phototransistors

Lead halide perovskites possess outstanding optical characteristics that can be employed in the fabrication of phototransistors. However, due to low current modulation at room temperature, sensitivity to the ambient environment, lack of patterning techniques and low carrier mobility of polycrystalline form, investigation in perovskite phototransistors has been limited to rigid substrates such as silicon and glass to improve the film quality. Here, we report on room temperature current modulation in a methylammonium lead iodide perovskite (MAPbI3) flexible transistor made by an extremely cheap and facile fabrication process. The proposed phototransistor has the top-gate configuration with a lateral drain–channel–source structure. The device performed in the linear and saturation regions both in the dark and under white light in different current ranges according to the illumination conditions. The transistor showed p-type transport characteristics and the field effect mobility of the device was calculated to be ~1.7 cm2 V−1 s−1. This study is expected to contribute to the development of MAPbI3 flexible phototransistors.

The Role of Au Doping on the Structural and Optical Properties of Cu2O Films

The changes in structural and optical properties of the Cu2O films obtained on the glass with different concentrations of Au by the chemical bath method were studied in this work. Lattice parameter, crystal size, preferential orientation and surface tension of the films were calculated using X-ray diffraction data which showed that all of the films were in polycrystalline form. It was determined that the structural parameters of all films were changed with the doping ratio. The surface morphology of the films was imaged using a field emission scanning electron microscope. The optical properties of the films were discovered using the optic spectrometer. Changes in the optical properties were discovered as a function of Au ratio. It was determined that the energy band gap value (2.12 eV-2.02 eV), the refractive index, the extinction coefficient, the real and dielectric coefficients, the optical conductivity, and the skin depth of films varied with Au doping ratio.

Synthesis, crystal structure, and vibrational studies of the monoclinically distorted double perovskite, Sr2Mn1−xNixTeO6 with (x = 0.25, 0.5, and 0.75)

The new double perovskite oxides Sr2Mn1−xNixTeO6 with x = 0.25, 0.5 and 0.75 have been synthesized in polycrystalline form by a conventional solid-state reactions process at 1180 °C, in the air. The structural and vibrational properties of these materials were studied by means XRPD, Raman, and IR spectroscopy. It has been proven that all the materials show typical double perovskite structures with a monoclinic symmetry, but with two different space group, P21/n for the compositions (x = 0.25 and 0.5), while the composition (x = 0.75) crystallizes in the space group I2/m. The lattice parameters obtained are in agreement with those of the two pure extremes Sr2MnTeO6 and Sr2NiTeO6. The monoclinic structural distortion involves long range ordering between Te6+ (in 2b site) and a random mixture (Mn2+/Ni2+) (in 2a site) for the two compositions (x = 0.25 and 0.5) that crystallize in P21/n. For the material (x = 0.75) with I2/m, similar distortion, ordering and mixing occur at the B and B’ double perovskite sites. It was observed that Vegard Law is satisfied, taking into account the cell parameters of both extremes. The effect of the partial substitution of Mn by Ni was also seen in Raman and IR data where a significant mode shift was observed with nickel content increase.

Structural, magnetic, electrical and dielectric properties of Pr0.8Na0.2MnO3 manganite

The orthorhombic Pr0.8Na0.2MnO3 ceramic was prepared in polycrystalline form by a Pechini sol–gel method and its structural, magnetic, electrical and dielectric properties were investigated experimentally.

High-Pressure Behaviour of Prussian Blue Analogues: Interplay of Hydration, Jahn-Teller Distortions and Vacancies

We report a high-pressure crystallographic study of four hydrated Prussian blue analogues: M[Pt(CN)6] and M[Co(CN)6]0:67 (M = Mn2+, Cu2+) in the range 0–3GPa. Mn[Co(CN)6]0:67 was<br>studied by single-crystal X-ray diffraction, whereas the other systems were only available in polycrystalline form. The Mn-containing compounds undergo pressure-induced phase transitions from Fm¯3m to R¯3 at 1.0–1.5GPa driven by cooperative tilting of the octahedral units. No phase transition was found for the orbitally disordered Cu[Co(CN)6]0:67 up to 3GPa. Mn[Co(CN)6]0:67 is significantly softer than the other samples, with a bulk modulus of 14GPa compared to 35GPa of the powdered samples. The discrepant pressure responses are discussed in terms of the presence of structural defects, Jahn-Teller distortions, and hydration. The implications for the development<br>of polar systems are reviewed based upon our high-pressure study.<br>

High-Pressure Behaviour of Prussian Blue Analogues: Interplay of Hydration, Jahn-Teller Distortions and Vacancies

We report a high-pressure crystallographic study of four hydrated Prussian blue analogues: M[Pt(CN)6] and M[Co(CN)6]0:67 (M = Mn2+, Cu2+) in the range 0–3GPa. Mn[Co(CN)6]0:67 was<br>studied by single-crystal X-ray diffraction, whereas the other systems were only available in polycrystalline form. The Mn-containing compounds undergo pressure-induced phase transitions from Fm¯3m to R¯3 at 1.0–1.5GPa driven by cooperative tilting of the octahedral units. No phase transition was found for the orbitally disordered Cu[Co(CN)6]0:67 up to 3GPa. Mn[Co(CN)6]0:67 is significantly softer than the other samples, with a bulk modulus of 14GPa compared to 35GPa of the powdered samples. The discrepant pressure responses are discussed in terms of the presence of structural defects, Jahn-Teller distortions, and hydration. The implications for the development<br>of polar systems are reviewed based upon our high-pressure study.<br>

Synthesis and Rietveld refinements of new ceramics Sr2CaFe2WO9 and Sr2PbFe2TeO9 perovskites

Ceramics of Sr2CaFe2WO9 and Sr2PbFe2TeO9 double perovskites have been prepared in polycrystalline form by solid-state technique, in the air. The crystalline structure was analyzed using X-ray powder diffraction (XRPD) at room temperature. Rietveld analysis of XRPD patterns show that both compounds adopt a tetragonal structure with space group I4/m, with unit cell parameters a = 5.5453(1) Å, c = 7.8389(1) Å for Sr2CaFe2WO9, and a = 5.5994(15) Å, c = 7.8979(30) Å for Sr2PbFe2TeO9. A certain degree of anti-site disordering of W and/or Te and Fe on the B –sites have been detected, indicating the presence of a partial amount of W and/or Te at Fe positions and vice versa.