Improving Quality And Stability Of Perovskite Films Through Interface Optimizing By Organic Amine

Organic-inorganic hybrid metal halide perovskite materials have attracted great attention recently due to their unique properties,such as adjustable band gap,high absorption coefficient and excellent carrier mobility.The photoelectric conversion efficiency（PCE）of perovskite solar cells（PSCs）has increased from 3.8%to 25.5%in recent years,which is close to crystalline silicon solar cells.The existence of trap states and/or ion defects limits the development of PSCs technology.Interface engineering can modify the surface and grain boundary by passivating molecules,and play an important role in passivating surface and/or grain boundary defects,reducing recombination centers and inhibiting ion migration.The interface layer not only inhibiting ion migration in the device but also prevent degradation and structural phase transition caused by moisture,heat and light,which enhancing the stability of the device.Based on above,this thesis systematically studies the influence of interface modification materials between perovskite and hole transport layer（HTL）on defects,the regulation of perovskite materials with different dimensions,and the efficiency and stability of devices.Specific research contents are as follows:1.Introducing three mixed halogenated isopentylamine IpAX（IpA=Isopentylamine;X=F,Cl,Br）as the interface passivation layer of PSCs devices,and their passivation ability was systematically studied by combining defect passivation and halogen engineering technology.Isoamyl amine cations can passivate organic vacancies and form2D perovskite layer,while X ions can passivate iodine vacancies and enter perovskite layer.We used different passivation layers formed by IpAF,IpACl or IpABr,and successfully inserted F into perovskite lattice by taking advantage of the solid solution formed by F in Cl or Br-based perovskite,and introducing Cl and Br at the same time.As a result,the decreased of the trap density and non-radiative recombination,which improve the efficiency of device when mixed halogenated amine IpAX-3（F:Cl:Br=2:1:2）was added into PSCs.The efficiency of device increased from 19.07%to 20.64%after IpAX-3modification,and the IpAX-3 passivated device retained 94%of the initial efficiency after100 h operation at MPP.2.This chapter uses the alkyl chain（Isoamylammonium IpA⁺）with a larger steric hindrance effect and the smaller aliphatic chain（Cyclopentylammonium CpA⁺）as interface additives,the effects of these two organic ammonium cations with different steric hindrances on the n value of perovskites were compared,and the effects of different types of 2D-3D perovskites and their devices on the photoelectric performance and stability were also studied.IpA⁺forms a quasi 2D-3D perovskite with n=2-5,and CpA⁺forms a strict 2D-3D perovskite with n=1.Compared with（CpA）₂PbI₄with n=1,the interlayer spacing of（IpA）₂MAPb₂I₇with n=2 is increased by 7.44?,which makes the dielectric confinement tend to decrease,resulting in the decrease of optical band gap and exciton binding energy,thus improving carrier transport,the PCE of the optimal device of quasi-2D-3D perovskite 21.12%,and the open circuit voltage(V_OC)is increased from the original 1.04V to 1.092V.The free energy of the film surface is reduced,caused by the steric effects and low polarity of alkyl chain,and the water molecules are inhibited from further penetrating into the perovskite film surface,which leads to a great improvement in the stability of quasi-2D-3D（1+）and naphthylmethyl amine（NMA⁺）,introduce NMA spacer cations into the perovskite lattice and form a 1D/3D perovskite heterostructure.The efficiency of the mesoporous PSCs device is significantly improved from 19.06%to21.18%,and the hydrothermal stability of the PSCs device is enhanced.XRD and XPS characterization show that NMA enters perovskite lattice.The top energy levels of valence band of the control and NMA devices are calculated to be-5.30 and-5.29 e V by combining UPS and UV-vis,which indicates that NMA modification reduces the energy level barrier between perovskite and Spiro-OMe TAD,which is beneficial to more effective interface charge extraction.Simultaneously 1D/3D heterojunction structure can effectively reduce non-radiative recombination caused by traps,and reduce interfacial charge recombination,further inhibit ion migration and improve the hygrothermal stability of devices.