Preparation And Characterization Of Perovskite Thin Film Solar Cell And Their Photoelectric Conversion Performance

Perovskite solar cell?PSC?is a kind of energy conversion device which uses perovskite energy storage materials as photoelectric conversion layers.The highest photoelectric conversion efficiency of currently certified perovskite solar cells is25.2%.The perovskite device is great significant for improving global environmental pollution and energy substitution issues.This dissertation mainly works in three aspects:the preparation and degradation of single crystal perovskite thin films,the ferroelectric polarization and ion migration of perovskite solar cells,and interfacial passivation of perovskite solar cells.Firstly,the single-crystal perovskite MAPbI₃ is grown on the mesoporous titanium dioxide substrate using a space-limited method with gradient temperature cooling.X-ray diffraction?XRD?and synchrotron radiation XRD confirmed tetragonal structure and single crystal.Scanning electron microscopy?SEM?image showed the single crystal perovskite MAPbI₃ is crack-free.Scanning transmission electron microscope?STEM?studies have shown that the perovskite MAPbI₃ is extremely sensitive to electron radiation,and is easily decomposed into lead iodide?PbI₂?.Part of the iodide ion of the MAPbI₃ is first lost to form the superstructure MAPbI_2.5,and then the structure continues to lose MA ions and additional I ions form MA_yPbI_2.5–z?0?y?1 and 0?z?0.5?.Finally,with the disappearance of the superstructure,PbI₂ with layered structures was formed.Secondly,the glass/c-TiO₂/CsFAMA/Spiro-OMeTAD/Ag perovskite solar cell was successfully prepared by a one-step liquid fabrication method,and obtained photoelectric conversion efficiency?PCE?of 20.11%.The ternary CsFAMA cation perovskite film has uniform grain size,compact surface without obvious cracks and holes.The high carrier transfer in device is ascribed to good crystallinity a suitable band gap,a suitable perovskite layer thickness and light absorption.The scanning probe microscope based on dynamic strain was employed to examine the simultaneous evolution of the ion distribution and spontaneous polarization of CsFAMA under light irradiation.The light illumination induced strong iron electrodeposition and slight ion migration.Ternary perovskite solar cell devices have a small hysteresis phenomenon.The current density-voltage hysteresis is not caused by ferroelectric polarization,but is ion migration.Finally,graphene oxide?GO?was successfully fabricated to reduced graphene oxide?rGO?by using argon at high temperature,and the interface of NiO_X and MAPbI₃ was effectively passivated by the reduced graphene oxide layer.The crystallization perovskite film on rGO substrate is flat and compact,and the perovskite grain size increased.The rGO passivation can increase the perovskite light absorption capability.This method effectively decreases the perovskite defect density states,suppresses the recombination of carriers,and increases the carrier life,resulting in the optimal photoelectric conversion efficiency of 19.44%and improved stability.