| Solar energy is the most representative green energy on Earth by its low carbon and reproducibility,and it has attracted extensive attention from worldwide scientists.As an outstanding representative of the emerging photovoltaic technology,organic-inorganic hybrid perovskite solar cells are slowly coming into the limelight with a series of advantages,such as rapid rising in efficiency,low preparation cost,simple fabrication process,and excellent photovoltaic performance.The perovskite photovoltaics have been recognized as one of the most promising competitors to replace silicon-based solar cells for commercialization by many academic and industrial circles.It is also one of the fastest-growing photovoltaic technologies up to date.However,there is still a long way to go before perovskite photovoltaic devices completely replace silicon-based solar cells.On the one hand,the mainstream tin-based oxide electron transport layer is not perfect.On the other hand,the toxicity of lead-based perovskites has hindered the further development of perovskite photovoltaics.Therefore,it is of great significance to improve the transport materials,develop low-toxic and lead-free perovskite materials,and further investigate the crystallization mechanism of perovskite films and develop efficient defect passivation strategy to prepare highly efficient and stable photovoltaic devices.To address the above issues,this dissertation provides specific research and discussion in the following chapters:In the second chapter,we have used TaCl5-doped SnO2 precursor solution to fabricate normal structure MAPbI3 perovskite solar cells.The pH value of the SnO2 precursor solution was changed after TaCl5 doping,which improved the hydrophobicity of the electron transport film and the affinity with the perovskite precursor solution.Thus,the grain size of perovskite thin-film became larger,and the defects were reduced,and the stability of the perovskite devices was improved.At the same time,the dopant regulated the conduction band position of the electron transport layer,which was more compatible with the energy level of the perovskite layer facilitating the electron transfer.Finally,the open-circuit voltage,as well as the power conversion efficiency of the corresponding perovskite photovoltaics,were increased.In the third chapter,tin perovskite films with different crystallinity were optimized by the mixed-solvents with different ratios of Dimethyl sulfoxide(DMSO)and N,NDimethylformamide(DMF).It verified that DMSO would directly coordinate with Sn2+to form SnI2ยท3DMSO in the precursor solution.As increasing the ratio of DMSO in the perovskite precursors,the perovskite grain size became larger,but the grain arrangements were not dense,which led to a poor-covered perovskite film with a rough surface.At the same time,the absorption spectrum of the tin perovskite film displayed a regular blue shift with an increased band gap.When the solvent ratio of DMF and DMSO was kept as 4:1,the fabricated perovskite film owned good light absorption intensity and maximum photoluminescence intensity.In addition,the crystallization mechanism of tin halide perovskite was analyzed,and the strategies of crystallization control were systematically summarized,which would guide the fabrication of highly efficient and stable and tinbased perovskite photovoltaics.In the fourth chapter,a multifunctional KSCN modification layer was introduced on the bottom surface of the tin-based perovskite layer to prepare FA0.75MA0.25SnI2Br-based photovoltaics.The KSCN interlayer optimized the energy level alignment in the device,improved the anti-oxidant performance,promoted the crystallization of perovskite with multiple crystallization orientations,reduced the trap density,and facilitated interfacial carrier transportation.As a result,the power conversion efficiencies of the KSCNmodified tin-based perovskite photovoltaic devices were significantly improved under both standard sunlight and indoor light. |
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