Studies On Functional Complexes Regulation To Achieve Highly Efficient And Stable Perovskite Solar Cells Assembly

The energy crisis and environmental pollution are the urgent issues to be solved.Solar energy,as clean and sustainable energy source,is the best candidate to replace the non-renewable fossil energy.So far,photovoltaic?PV?technology is an effective method to directly convert sunlight into electricity.Solar cells based on silicon?Si?,gallium arsenide?GaAs?,cadmium telluride?CdTe?,and copper indiumgallium selenide?CIGS?,have achieved efficiency over 20%,however,all these devices have deficiencies in their commercialization.Perovskite solar cells?PSCs?as a rising star in photovoltaic field,in the past ten years,the power conversion efficiency?PCE?of PSCs has been rapidly improved from an initial value of 3.8%to a recent world record value of 25.2%,almost matching with mainstream polycrystalline silicon.Especially,low-temperature solution processability of perovskite film offers a promising route toward cheap electricity generation using sunlight,which is beneficial to the commercialization.But the fabrication of perovskite film by low-temperature solution is far from thermodynamic equilibrium,usually causing the formation of polycrystalline structure.This inevitably results in various defects in perovskite film,which would continuously induce device decomposition,limiting their practical application.The work of this thesis is mainly focus on designing complexes and endowing complexes special property,then using these functional complexes to chemical modify the perovskite film,further improving the stability and performance of the PSCs.The thesis will be divided into six chapters,see as follows:Chapter 1:Firstly,the composition and property of perovskite as well as the structure and working principle of perovskite solar cells are presented.Based on this,the development process and the main problems of the perovskite solar cell as well as the solutions reported in literatures are summarized.Finally,the purpose and significance of this paper are put forward to solve current problems.Chapter 2:We synthesized the Eu-Complex and directly doped into the perovskite precursor,which could efficiently inhabit the light degradation of perovskite film due to the Eu-Complex possesses strong absorption in ultraviolet region.In addition,the formation of hydrogen bonds between the organic cation from perovskite and-CF₃ from the Eu-Complex,which is beneficial to restrain the escape organic cation and improve the thermal stability.The Eu³⁺from Eu-Complex could oxidize Pb⁰ into Pb²⁺,then formation of Eu²⁺which could reduce I⁰ to I^-under the heat and light stress,thus decreasing the defects Pb⁰ and I⁰.Furthermore,the aromatic ligand could reduce or capture the trace amount of I⁰ existing as electronic defects in perovskites.The results indicated that the heat and light stability of perovskite solar cells could be improved through making full use of the structural design and properties of the ligands and metal ions.Chapter 3:The formation of defects at surfaces and grain boundaries?GBs?during the fabrication of solution-processed perovskite film are thought to be responsible for its instability.We synthesized the Eu-porphyrin complex?Eu-pyP?and directly doped into methylammonium lead triiodide?MAPbI₃?precursor,perfectly fabricating 2D?Eu-pyP?_0.5MAn-1Pb_nI_3n+1 platelets inlaying the grain boundaries of 3D polycrystalline interstices in this protocol.The Eu-pyP complex could convert the UV light into visible light which could enhance light stability.Moreover,the thermal and light stability are attributed to the formation of 2D perovskite.Consequently,the Eu-pyP modified PSCs could synchronously improve resistibility to moisture,heat,and solar light including UV.Chapter 4:Employing all-inorganic perovskite quantum dots?QDs?to treat the organic-inorganic perovskite film has well-documented as an efficient strategy to improve the performance and stability of perovskite solar cells.However,the insulating molecules-coated QDs with zero dimension?0D?structure would inconducive to charge transfer.Here we employ a conductive diammonium porphyrin?ZnPy-NH₃Br?to treat CsPbBr₃ QDs coated on 3D perovskite film,thus constructing a stable 0D-2D perovskite capping layer.The formed capping layer can achieve efficient charge transport,finally,the performance and stability of PSCs enhanced.Chapter 5:The I^-and Pb²⁺ions of perovskite would produce ineluctably reaction and form the defects,leading to the degradation of the perovskite films.To address this problem,we synthesized and doped the CoTPPS into the perovskite solution.The results indicated that Co²⁺of CoTPPS could reacte with I₂ which generated under the thermal and light condition,producing the Co³⁺and I^-,achieving the regeneration of I^-in perovskite film.Moreover,the sulfonic group could coordinate with Pb²⁺,and thus passivating the uncoordinated Pb²⁺defect.Therefore,the CoTPPS modified PSCs efficient reduced defects and inhibited charge recombination,finally,the efficiency and light as well as heat stability improved.Chapter 6:The work summary and prospects of this thesis.