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Solution-processed mixed halide CH3NH3PbI3−xClx thin films prepared by repeated dip coating

Karim, A. M. M. Tanveer, Hossain, M. S., Khan, M. K. R., Kamruzzaman, M., Rahman, M. Azizar, Rahman, M. Mozibur
Journal of materials science 2019 v.54 no.18 pp. 11818-11826
X-ray diffraction, absorbance, ambient temperature, chemical bonding, coatings, crystals, emissions, energy, photoluminescence, scanning electron microscopy
The mixed halide CH₃NH₃PbI₃₋ₓClₓ crystalline thin film has been prepared by two-step solution-processed repeated dip coating method at an ambient atmosphere. X-ray diffraction study reveals the presence of tetragonal and cubic phases in deposited film. Raman study confirms the metal halide bond in the inorganic framework and organic CH₃ stretching/bending of C–H bond in CH₃NH₃PbI₃₋ₓClₓ perovskite. Scanning electron microscopy shows that cuboid and polyhedral-like crystal grains of 100 nm to 2 μm may find applications in optoelectronics. The perovskite CH₃NH₃PbI₃₋ₓClₓ thin film shows high spectral absorption coefficient of the order of 10⁶ m⁻¹. In optical band gap study, we found the coexistence of cubic and tetragonal perovskite phases. The energy band gap is dominated by cubic phase having Eg = 2.50 eV over tetragonal phase with band gap Eg = 1.67 eV. The room-temperature photoluminescence study confirms band edge, shallow and deep-level emissions. The temperature-dependent cathodoluminescence study shows red, green and ultraviolet emissions. The dominating green luminescence evolved for cubic phase at 2.51 eV. The red and ultraviolet emissions are also found for mixed-phase CH₃NH₃PbI₃₋ₓClₓ thin film, suitable for preparation of light-emitting devices.