Research And Improvement On The Stability Of Two-Dimensional Organic-Inorganic Lead-Based Hybrid Perovskite

Organic-inorganic lead-based hybrid perovskite solar cells(PSCs)have been rapidly developed in recent years.During the past eight years from 2009 to 2017,the power conversion efficiency(PCE)has soared from 3.8%to 22.10%,which is much faster than other commercial solar cells(SCs).Although gratifying breakthroughs have been achieved,two major issues,which are long-term instability and toxicity of lead,have become the hugest bottlenecks for practical applications.Substituting lead with other environmental-friendly metals can be used as a solution to to resolve the problem of toxic harmfulness,but the performance of lead-free PSCs is less than satisfactory.Actually,the toxic harmfulness is closely related to its own instability,which is majorly derived from the degradation of lead-based perovskites in humid environment.If the stability problem of perovskite material is is solved,even if it contains lead element,it will not cause any harm to humans and the environment.Aiming at the instability of PSCs in the humid environment,in this paper,a simple solution-processing strategy that uses a bifunctional organic molecule(glycine)was proposed and demonstrated for the dehydration condensation between functional groups to improve the moisture stability of 2D hybrid perovskites.The detailed work as follows:(1)The first chapter mainly introduces relevant background knowledge,including the development history,the battery structure and working principle of the PSCs;the structure,properties and application of perovskite material;the preparation technology of the perovskite material;the degradation mechanism,stability improvement measures and the challenges of PSCs.(2)The second chapter mainly discusses the experimental part of the research.The instruments,reagents and materials are described,as well as the synthesis and preparation methods.X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),UV-vis-NIR absorption spectroscopy,X-ray photoelectron spectroscopy(XPS),Raman spectroscopy and the stability tests are described.(3)The third chapter mainly describes the research process and discusses the related experimental results in detail.Firstly,the GLy2PbI4 and GLy2PbI4-DCC films were prepared,and the crystal structure,morphology,spectrum,and electronic binding energy of the films were characterized by XRD,SEM,TEM,UV-Vis-NIR and XPS,respectively,the stability was characterized by accelerated moisture-tolerance tests.The moisture-tolerance test results show that the GLy2PbI4 film degrades immediately and generated PbI2 after encountering with water vapor,while the GLy2PbI4-DCC film show no obvious change.XPS results show that the-COOH and-NH3+ of the GLy molecule form a stable-CO-NH2+ bond through dehydration condensation,which is the main reason for its improved stability.