Interfacial Regulation And Photovoltaic Performance Of Mixed Cation-based Lead-halide Perovskite Thin Films

Organometallic halide perovskite（PVSK）,as a new type of optoelectronic core material,has been widely used in optoelectronic devices,such as perovskite solar cells（PSC）,photodetectors and light-emitting diodes.At present,the certified power conversion efficiency（PCE）of PSC has approached 26%,which has become one of the new generation photovoltaic technologies with the most potential to replace traditional solar cells.However,in the process of its commercial application,it still faces key challenges such as energy loss and long-term stability.Improving the quality of perovskite films and optimizing the device interface are effective means to address the above issues.Therefore,the scientific problems existing in the thin film preparation,defect passivation,interfacial carrier transport and recombination mechanism,and device humidity/thermal stability of mixed cation-based lead halide perovskites were systematically studied in this thesis.Efficient and stable p-i-n-type planar PSCs were constructed,and the mechanism of interfacial regulation of mixed cation-based lead-halide perovskite thin films to improve cell efficiency and stability were revealed.The main innovative achievements of this thesis are as follows:1.The bilateral interface optimization of the bication-based perovskite film effectively improves the film quality,device efficiency,and humidity stability.A new strategy for simultaneous optimization of the two interfaces of poly-TPD/PVSK and PVSK/C₆₀ using amphiphilic conjugated polyelectrolyte（PFN）and non-fullerene acceptor molecule（ITIC）,respectively,is proposed.The hydrophilicity of poly-TPD layer is enhanced,ITIC not only improves the hydrophobicity of the film surface but passivates the grain boundaries and surface defects of the film,and further resulting in a compact perovskite film,and the high-quality(FA_1-xMA_xPb I_3-2yBr_yCl_y,FAMA)double-cation-based perovskite films and efficient and stable PSCs were prepared.The value of device efficiency was increased from 18.7%to 20.5%through BIE technology,and the open circuit voltage(V_OC)was increased from 1.077 V to 1.124 V,while the energy loss of the device was significantly reduced to only 0.38 e V;After collaborative optimization with PFN and ITIC,84.7%of the initial efficiency was maintained after 300 h of storage under the ambient condition with a relative humidity of 55±5%,resulting in reduction of PCE loss under high humidity.2.The triphenylamine:polystyrene（TPA:PS）hybrid layer significantly reduces the energy loss and improves humidity stability of bication-based perovskite solar cells.Based on the Lewis acid-base theory and the tunnel junction principle,a new method for regulating the perovskite/C₆₀interface using a TPA:PS blending layer is proposed.The hydrophobicity of the film surface and the interfacial contact were improved by using the TPA:PS hybrid layer improves,the mechanisms of using Lewis acid-base interaction between the lone pair electrons in TPA and Pb²⁺ions to enhance carrier transport and suppress carrier recombination at the perovskite/C₆₀ interface is elucidated.The device efficiency was increased from 18.8%to 21.8%after optimization with the TPA:PS mixed layer,V_OC was increased from 1.047 V to 1.153 V,and energy loss was decreased from 0.49 e V to 0.35 e V;The hydrophobic layer of the TPA:PS interface improved the moisture resistance of the device.The device efficiency still maintained more than 91%of the initial PCE value after 10-days storage in the air environment（RH=40～60%）,effectively reducing the efficiency loss under high humidity.3.Structural manipulation of trication-based perovskite films achieves simultaneous improvement of device efficiency and stability.It is proposed to use imidazolyl sulfonate ionic liquids（BMIm OTs）to control the perovskite crystallization process to form perovskite films with larger grain size and higher surface hydrophobicity.The additive is located at the grain boundaries of the perovskite film,thereby significantly passivate Pb²⁺ions and Pb⁰ defects localized at grain boundaries,improving interfacial carrier transport efficiency.The efficiency value of the device with BMIm OTs treatment was increased from 19.1%to 20.7%,and the V_OCwas also increased from 1.095 to 1.128 V;After modification by BMIm OTs,87.6%and 89.2%of the initial efficiencies were maintained after 400 h of storage at 85°C in an N₂-filled glovebox and 400 h of storage under the ambient condition with a RH of 55±5%,respectively,which significantly reduced the efficiency loss in a humid and high-temperature environment.4.Crystallization regulation and defect passivation of trication-based perovskite films contribute to the synergistic improvement of cell efficiency and thermal stability.A new idea is proposed to use butylammonium acetate（BAAc）multifunctional additive to modulate the precursor solution,passivate defects and control the crystallization process of trication-based perovskite.The chemical bond interaction mechanism for the formation of C=O-Pb chelate bonds and N-H···I hydrogen bonds between BAAc and the precursor and film was revealed,and The regularity of using BAAc additive to retard the crystallization rate of Cs FAMA perovskite and increase he grain size is elucidated,and a high-quality trication-based perovskite film with better preferred orientation and more stable crystal structure was obtained,which reduced the interfacial carrier recombination loss.Introduction of BAAc resulted in a more thermally stable Cs FAMA perovskite films at 85°C;The device efficiency was increased from18.6%to 20.2%after BAAc treatment,and V_OC was also increased from 1.089 V to 1.120 V;More importantly,after 700 h of aging at 85°C in the nitrogen environment and 650 hours storage in the ambient condition with a RH of 35±5%,the BAAc-treated devices were shown to be much more excellent stable as maintained 79.5%and 76.3%of the initial power conversion efficiency,respectively,leading to a more stable device under humidity/thermal environment.This thesis not only provides an effective interface optimization and crystallization regulation for reducing energy loss and improving device lifetime,but also elucidates the mechanism of different regulation strategies,providing new ideas for interface and additive engineering technologies,and experimental and theoretical support is further provided to design and build high-performance PSC.