Perovskite solar cells continue to attract strong attention because of their unprecedented rate of power conversion efficiency increase. CHNHPbI (MAPbI) is the most widely studied perovskite. Typically one-step (1-s) or two-step (2-s) deposition methods are used to prepare MAPbI films. Here, we investigate a new MAPbI film formation method that combines 1-s and 2-s deposition (termed 1 & 2-s) and uses systematic variation of the stoichiometric mole ratio (x) for the PbI + xMAI solutions employed. The PbI + xMAI solutions were used to deposit precursor films that were subsequently dipped in MAI solution as a second step to produce the final MAPbI films. The morphologies of the 1 & 2-s MAPbI films consisted of three crystal types: tree-like microcrystals (≫1 μm), cuboid meso-crystals (∼0.1-1 μm) and nanocrystals (∼50-80 nm). Each crystal type and their proportions were controlled by the value for x. The new 1 & 2-s deposition method produced MAPbI films with tuneable optoelectronic properties that were related to those for the conventional 1-s and 2-s films. However, the 1 & 2-s film properties were not simply a combination of those for the 1-s and 2-s films. The 1 & 2-s films showed enhanced light scattering and the photoluminescence spectra displayed a morphologically-dependent red-shift. The unique morphologies for the 1 & 2-s films also strongly influenced PbI conversion, power conversion efficiency, hysteresis and recombination. The trends for the performance parameters and hysteresis were compared for devices constructed using spiro-MeOTAD and P3HT and were similar. The 1 & 2-s method should apply to other perovskite formulations and the new insights concerning MAPbI crystal growth conditions, morphology and material properties established in this study should also be transferable.
Five new carboxylic acid precursors bearing thiourea group and their corresponding bismuth(III) complexes were synthesized and characterized using CHNS and inductively coupled plasma analyses and infrared and NMR ( 1 H, 13 C) spectroscopies. Single-crystal X-ray diffraction analysis was also carried out for one of the precursors. The behaviour of the compounds was bioassayed for antibacterial, antifungal, antioxidant and enzyme (lipoxygenase, α-glycosidase and anti-urease) inhibition activities. It is concluded that the interaction of the compounds with bismuth enhances both the antimicrobial and enzyme inhibition activities. The synthesized compounds may prove to be good therapeutic agents.
Chalcogenide amorphous thin films of the modification (As 2 S 3 ) 0.95 Cu 0.05 were prepared using a thermal evaporation technique. The optical properties of the resultant films were investigated based on the transmittance spectra in the photon energy range 1.6-2.82 eV. Thicknesses of the films under study were determined using the envelope technique based on the transmittance spectra. The optical measurements were carried out over the conditional temperature extending from 77 to 300 K. The results of the mentioned measurements are conductive tools in investigating the electronic structures of the Chalcogenide Glasses, however the analysis of the experimental results provide information about the optical gap width and elucidate the broadness of the band tail that may disturb the band gap edges. Moreover, the single-effective oscillator was implemented in calculating both the oscillation and dispersion energies of the films under investigation. The static refractive index and the static dielectric constant were also determined for these films.
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