Synthesis and structural, crystallographic, electronic, chemical and optical characterizations of alpha-diisopropylammonium bromide (α-DIPAB) thin films

Thin films of the promising Diisopropylammonium Bromide (α-DIPAB) are synthesized by the slow evaporation technique. We report on the synthesis and characterization of as-grown (α-DIPAB) thin films. In particular, structural, crystallographic, electronic, chemical, and optical properties are measured and interpreted. To elucidate structural and crystallographic properties, X-ray diffraction (XRD) measurements are conducted to reveal that α-DIPAB thin film is polycrystalline and exhibits a monoclinic structure. Furthermore, Density Functional Theory (DFT)-based simulations are performed to calculate the structural and electronic parameters of the α-DIPAB thin film. An excellent agreement between the measured and calculated structural parameters is obtained. Taking into account the Van der Waals forces using the HSE06 method yields an optical band gap (≈6 eV) in good agreement with the experimental value. Scanning Electronic Microscopy (SEM) micrographs demonstrate that thin-film surface cracks appear dividing the surface into ice land-like regions. The coarse features in the short-scaled micrograph are characterized by the micro-sheet-like with cracked boundaries. Moreover, the role of the interactions between molecules mediated by bromine ions is revealed. The vibrational spectra correspond to a well-ordered crystal. The mechanism behind the large spontaneous polarization of thin films is explained. The interplay between electronic and optical properties of thin films is investigated using UV-Vis measurements and the recently published mathematical derived model. An excellent agreement between measured and calculated electronic and optical parameters indicates the validity and feasibility of the model.