Study On Fabrication Of Methylamine Lead Iodine Perovskite Solar Cell Thin Films

In recent years,due to the potential value of scientific research and commerce,organic-metal halide perovskite solar cells had received extensive attention.Organic-metal halide Perovskite thin film layer,not only acts as the active layer to absorb light energy,but also has the ability to transmit holes and electrons.A variety of methods for preparing high quality organic-metal perovskite thin films have been found,and one-step solution method is widely used because of its simple operation.In this paper,one-step solution method was used to prepare the films,and the physical and chemical properties of the films were investigated under different conditions.Details are as follows,(1)Fabrication and properties characterization of methylamine lead iodine perovskite thin films in different blending proportion systems.The thin films were prepared in one-step method,and the molar ratio of Pb I2 and CH3NH3 I was 1:1,1:1.5 and 1:2,respectively.It turned out that they had the same absorbing boundaries,and the crystallinities were similar,too.Comparing with the equimolar,the crystal size of the organic-metal halide perovskites were much larger when CH3NH3 I was joined excessively.The crystal size was 0.2 μm when the molar ratio of Pb I2 and CH3NH3 I was 1:1,and the values were 1.5 μm and 1 μm when the ratio was 1:1.5 and 1:2,respectively.(2)Effects on phase transition of methylamine lead iodine perovskite thin films during thermal annealing.Methylamine lead iodine perovskite thin films had semblable phase transition process in different blending proportion systems.During heating procedure,it demonstrated that there was totally phase transition from tetragonal to cubic at 60 ℃.When cooled back to room temperature,the phase reversally transited from cubic to tetragonal partially.It showed that the phase transition of organic-metal halide perovskite was reversally,and the cubic was the metastable phase,the tetragonal one was more stable at room temperature.(3)Variation of the methylamine lead iodine precursor thin films during aging and its influence on the subsequent perovskite thin films.The methylamine lead iodine precursor thin films had gradually turned from ash black to dark brown after aging for a time at room temperature.There was no doubt that the films appeared to be black after annealing.Principles were investigated comprehensively by using the X-ray diffraction intensity,UV-Vis absorption and AFM surface morphology.With the aging time increasing at room temperature,MAPb I3 precursor was disappearing,more MAPb I3 perovskite generated and finally reached a stable value while some precursor still left.Comparing with the two annealing results,the X-ray diffraction intensity and UV-Vis absorption of methylamine lead iodine precursor films as prepared were higher than the films after aging,and the AFM surface morphology after thermal annealing showed that the crystalline grain size of thin film made from as prepared precursor films was much bigger than that made from aged precursor thin films.The research in this paper provides new ideas and direction for the study of preparation methods,formation mechanism and basic characteristics of methylamine lead iodine perovskites,and it may have a certain guiding values in the study and application of the organic-metal halide perovskite solar cells or the involved photoelectronic devices.