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 (PbI2) thin films as the underlying layer. The dip-coating method used involved immersion of a slowly rotating substrate in the required solution. The PbI2 film was immersed into methylammonium iodide (MAI) solution in 2-propanol for 10-60 min. The MAPbI(3) films were thermally annealed at 85 degrees 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 780nm, equivalent to a bandgap energy of 1.55eV, assigned to the MAPbI(3) with optical absorption coefficient of 10(5) cm(-1).