The Effect Of Hydrogen Halide And Ammonium Hydroxide As Additive On The Morphology And Charge Transfer Of Perovskite Films

The emerging of perovskite solar cells has achieved satisfactory accomplishment in recent years,benefited from its high charge carrier mobility,suitable band gap and high molar extinction coefficient.As the sensitizer and the most important element of perovskite solar cells,the quality of perovskite films has decisive impact on the performance of the solar cells.Obtaining high quality perovskite films is the most attractive research among the community.To obtain high quality perovskite films,we add some suitable additives into the precursor solution.Hydrogen halide is added into the precursor solution with a certain volume ratio.The morphology and crystallinity of resultant perovskite films are enhanced obviously and the power conversion efficiency of the perovskite solar cells is increased from 9.66%to 15.2%.Utilizing anti-solvent and characterizing the component by XRD and Fourier transform infrared spectroscopy,we find a new intermediate MAI-PbI2-DMF-xHX(X=Cl,Br,I).Then,we give reasonable explanation of the effect of hydrogen halide additive according to the crystallizing theory.In addition,we chose the basic ammonium hydroxide as additive,the morphology and crystallinity of the fabricated perovskite films are being enhanced,and the power conversion efficiency being increased to 13.5%.In order to enhance the power conversion efficiency of perovskite solar cells,we must optimize the structure and materials of perovskite solar cells based on a deep understand of charge transfer.Via time resolved transient absorption,we studied the effect of the perovskite film quality on charge recombination in perovskite films and at interface.We found that the dominate charge recombination in high quality perovskite films was the direct charge carrier recombination,and the charge recombination between electrons in conduction band of TiO2 and holes in valence band of Spiro-OMeTAD was suppressed.More Over,we studied the charge recombination between electrons in conduction band of TiO2 and holes in valence band of perovskite,electron in conduction band of perovskite and holes in valence band of Spiro-OMeTAD.The timescale of these recombination were about 100-300 ns.As a result,our research can provide a helpful method to evaluate the quality of perovskite films and make a clear understanding of charge transfer in perovskite solar cells.