Synthesis And Application Of Inorganic Ternary Semiconductors In Perovskite Solar Cells

Since 2009,the power conversion efficiency（PCE）of perovskite solar cells（PSCs）based on hybrid organic-inorganic perovskite materials has been improved very fast from 3.8%to 22.7%in just a few years.PSCs have presented great application prospects.PSCs are mainly consisted of electron transport layer（ETL）,perovskite light absorber layer,hole transport layer and so on.As discovered in previous research,there are many factors that affect the stability of PSCs.The materials and structures of every functional layers can influence the stability of PSCs.In order to increase the stability of PSCs,we mainly focused on the electron transport materials（ETMs）and perovskite materials which have a greater impact on the stability.（1）In the aspect of ETMs of PSCs,the strong photocatalytic activity of the most widely used TiO₂ will induce the photodegradation of perovskite materials.To solve this issue,it is the first time to propose the application of inorganic ternary perovskite barium stannate BaSnO₃（BSO）as the replacement of original TiO₂ mesoporous ETM.The BaSnO₃ has many remarkable optoelectronic properties,weak photocatalytic activity,high electron mobility and no phase change.By synthesizing highly dispersed BSO nanoparticle paste and forming fine BSO mesoporous ETL,the BSO based PSCs showed comparable photovoltaic performance to the TiO₂ based PSCs.It proves that the feasibility of using inorganic ternary semiconductors instead of the original ETMs.Then,due to the adjustable compositions and doping modification properties of BSO,the lanthanum doped BaSnO₃（LBSO）was applied as ETM in PSCs.The fabricated novel LBSO based PSCs obtained effectively improved light soaking stability without sacrificing the photovoltaic performance of the devices.（2）In the aspect of light absorber materials,perovskite light absorbers have poor stabilities.Especially for the classical CH₃NH₃PbI₃,it is sensitive to light,heat and humidity conditions and easy to decompose.Chemically stable,non-toxic and environmentally friendly bismuth-based perovskite light absorbers are novel perovskite materials with research value.The inorganic ternary perovskite material Cs₃Bi₂I₉ was prepared via a simple and easy-to-handle method with mild conditions.Compared with the traditional preparation method,the film morphology was effectively improved.Higher efficiency and good long-term stability of the devices were obtained.In addition to the perovskite structure light absorbers,by referring and analysing the properties of perovskite light absorber materials and devices such as photoelectric properties,energy band structure,and charge transport mechanism,a novel inorganic ternary light absorber Ag₈SnS₆（ATS）was screened out and synthesized.ATS has great photoelectric properties and is non-toxic,non-polluting and chemically stable.Devices based on ATS have exhibited a potential PCE and outstanding long-term stability.In this thesis,device defects and instability caused by original functional materials in PSCs were investigated and relieved by screening,synthesizing and applying novel inorganic ternary semiconductors in PSCs to replace the original functional materials.These works relieved the limitation of the original functional materials in PSCs and can provide guidance and ideas for the application of novel functional materials in PSCs.