Effect of Speed of Spin Coating Deposition on Properties of CH3NH3PbI3 Organic- Inorganic Halide Perovskite

Lead halide perovskites have attracted considerable interest over the last few years as photo absorbers in photo voltaic applications with record efficiencies now reaching 22%. Organic-inorganic halide perovskite based solar cells have been prepared by means of sequential spin-coating process. The spin-rate and step for PbI2 as well as its concentration are important in determining the surface morphology of perovskite, and consequently, J−V performance. Perovskite absorber layer has been deposited by spin-spin process in which both lead iodide and methylammonium iodide precursors were deposited by spin coating. Methylammonium iodide has been deposited by one step and two step spinning program. One step deposition rate was 3000 rpm and two step deposition rate varied from 3000 to 5000 rpm in second step. TiO2 substrates preparation, lead iodide deposition, and annealing condition was maintained constant for all samples. X-ray diffraction (XRD) and scanning electron microscopy (SEM) have been used to understand the importance of spin-coating parameters in perovskite solar cells. Addition of deposition steps caused the formation of a relatively uniform perovskite layer and decreased grain size. Increasing spinning rate increased crystallinity and full conversion of perovskite. Thus, fully conversion of precursors to ideal perovskite tetragonal crystal structure at room temperature was obtained by increasing deposition step and speed of spinning deposition