Preparation, Structure And Optical Properties Of Methylammonium Lead Iodide Perovskite Absorber

Perovskite solar cell based on methylammonium lead iodide (CH3NH3PbI3) perovskite absorber has developed rapidly in recent years and the efficiency raised from the original 3.8% to 20.2%. CH3NH3PbI3 is a direct band gap semiconductor with a broad spectral absorption and excellent carrier transport properties, very suitable for solar cell absorber.In this paper, we prepared CH3NH3PbI3 thin film on mesoporous TiO2 electrode with one-step and two-step solution method。 And we research the Influences of main process parameters on the film structure, morphology and optical properties. Using the X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) characterize the structure, morphologies, composition distributions and characterize absorption properties with UV-visible spectrophotometer (UV-Vis)Observed the thin film prepared by one step method annealing at different temperatures, found the coverage of CH3NH3PbI3 film prepared on TiO2 electrode is low, increasing the annealing temperature caused the film to shrink, and further reduce the coverage.In order to improve the coverage of the film on the electrode, we used a two-step method to prepare CH3NH3PbI3 thin film, and found there is high PbI2 impurity in thin film. By adjusting the speed of the spin coating, annealing temperature and PbI2 precursor concentration to optimize experimental conditions. The results show that increasing the concentration of PbI2 precursor is beneficial to improve the nucleation density of CH3NH3PbI3 and increase the surface coverage of thin film. In addition, PbI2 films soaked in thermal CH3NH3I can promote the transformation from PbI2 to the perovskite phase, and obtain CH3NH3PbI3 film without PbI2 impurity.