Structural and Optical Properties of Two-Step Dip-Coated CH3NH3PbI3 Films Based on Underlying Dip-Coated PbI2 Films

Thin films of methylammonium lead iodide (MAPbI 3 ) were deposited on glass slides under various preparation conditions by a two-step dip-coating method, using dip-coated lead iodide (PbI 2 ) thin films as the underlying layer. The dip-coating method used involved immersion of a slowly rotating substrate in the required solution. The PbI 2 film was immersed into methylammonium iodide (MAI) solution in 2-propanol for 10–60 min. The MAPbI 3 films were thermally annealed at 85 °C for 10–30 min. Fundamental properties of the annealed MAPbI 3 films were studied by x-ray diffraction (XRD), scanning electron microscopy (SEM) and ultraviolet-visible spectrophotometry. The XRD patterns and SEM micrographs revealed single tetragonal-phase structure, with diffraction peaks became intense and narrow with increasing dipping times and upon thermal annealing. Transmittance spectra of these MAPbI 3 film/glass systems declined steeply near 780 nm , equivalent to a bandgap energy of 1.55 eV , assigned to the MAPbI 3 with optical absorption coefficient of 10 5 cm - 1 .