Study On The Microstructure And Chemical Composition Of Perovskite Absorption Layer And Influence To The Photovoltaic Performance Of Perovskite Soalr Cells

Perovskite absorption layer was the most important part of the perovskite solar cells, and it had been heated researched during recent years. In this thesis, a two-layer structured PbI2 thin film was successfully constructed by spin-coating and close-spaced vacuum thermal evaporation sequential deposition, and then transformed into a perovskite thin film by treating with CH3NH3I vapor. The crystal structure, bandgap and surface morphology of the perovskite thin film were characterized. Moreover, the perovskite solar cells with the architecture of FTO/c-TiO2/CH3NH3PbI3/spiro-OMeTAD/Au were fabricated. The photovoltaic performance of the corresponding perovskite solar cells was compared. The PbI2-DMSO thin film was obtained via spin-coating the solution of Pb12-DMSO with the addition of equal molar DMSO in the DMF solution, and transformed to prepare the CH3NH3PbI3-xBrx thin film by spin coating with different ratios of CH3NH3I and CH3NH3Br in the isopropanol, which achieved successfully the Br doping in CH3NH3Pbl3-xBrx thin films. The corresponding perovskite solar cells were assembled, and the chemical composition, crystal phase, optical band gap and surface morphology of the CH3NH3Pb13-xBrx thin films were characterized. The two-layer structured Pb12 thin film was converted to CH3NH3Pb13-xBrx and CH3NH3Pb13-xClx thin films via treating with CH3NH3Br and CH3NH3C1 vapor, respectively. The influence of the two kinds of perovskite thin films on the chemical composition, crystal structure, bandgap and surface morphology of the perovskite thin films was investigated. The photovoltaic performance of the fabricated solar cells with the structure of FTO/c-TiO2/CH3NH3PbI3-xXx/spiro-OMeTAD/Au was estimated.The results revealed that a two-layer structured PbI2 thin film was successfully constructed by spin-coating and close-spaced vacuum thermal evaporation sequential deposition. The thickness of the corresponding bottom and top MAPbI3 thin film was 180 nm and 220 nm, respectively. The two-layer perovskite thin film was consisted of the bottom CH3NH3PbI3 thin film of 180 nm-thick with compact and pinhole-free, which was beneficial for suppressing the charge recombination of the electrons of the TiO2 conduction band and the holes of the spiro-OMeTAD valence band, and the top CH3NH3Pb13 thin film of 220 nm-thick with porous, which was beneficial for improving the hole migration from the perovskite to spiro-OMeTAD and the charge separation at the perovskite/spiro-OMeTAD interface. The planar perovskite solar cells based on the two-layer structured Pb12 thin film exhibited the best the photovoltaic conversion efficiency (?) of 11.64%. The PbI2-DMSO complex thin film was successfully prepared by spin-coating PbI2 solution of DMF with the addition of equal molar DMSO. The XRD showed that the peak position shifted from 2?=12.67° to 20=9.65°. The CH3NH3PbI3-xBrx thin films with different chemical composition were achieved by spin-coating CH3NH3X solution with various ratios of CH3NH3I and CH3NH3Br. The result of EDS, XRD and UV-Vis absorption spectra jointly showed Br doping in perovskite thin films can be successfully achieved by spin-coating CH3NH3X solution. However, the content of Br in the perovskite thin film was not increased with the ratio of CH3NH3Br in the CH3NH3X solution increased. The assembled solar cell with molar ratio of 5% of the CH3NH3Br mixed solution processing gave a best ? of 13.20% with a Voc of 1.02 V, a Jsc of 17.77 mA cm-2 and a FF of 72.77%. The two-layer structured PbI2 thin film was converted to CH3NH3PbI3-xBrx and CH3NH3PbI3-xClx thin films via treating with CH3NH3Br and CH3NH3C1 vapor. The result of characterization indicated that the perovskite thin film was uniform and compact and the thicknesses of CH3NH3Pbl3_xBrx and CH3NH3PbI3-xClx thin films with vapor treatment 65 min and 40 min were 260 nm and 430 nm, respectively. Furthermore, the results of EDS, XRD and UV-Vis absorption spectra show that the two kinds of thin films were successfully doped. The photovoltaic conversion efficiency (77) of 5.98%and 4.41% were achieved by the perovskite solar cell with the two kinds of thin films, respectively.