| As the next generation of the most promising photovoltaic materials,organic-inorganic lead halide perovskite has attracted great attention.With the efforts of researchers,the best-performing power conversion efficiency(PCE)of organic-inorganic hybrid lead halide perovskite solar cells(PSCs)has already increased from initial 3.8%to 25.2%within just a few years,which is comparable to the efficiency of polycrystalline silicon cells.However,the toxicity issue of lead is a bottleneck limiting the commercial development and large-scale application of Pb-based PSCs.Among the potential alternatives,Sn-based perovskites stand out from other candidates for their superior optoelectronic properties,which contain optimal optical band gap(1.2-1.4 eV),high light absorption coefficient,low exciton binding energies and extremely high charge carrier mobility.However,it is full of challenge to fabricate uniform and pinhole-free Sn-based perovskite films for the fast and unmanageable crystallization of the films and the facile oxidation of Sn2+,which is an urgent problem to be solved.In this thesis,formamidine tin iodide(FASnI3)perovskite has been chosen for the fabrication of PSCs.Efforts have been devoted to improve the problems of film formation and device stability,which are as followsFirst of all,we selecte FASnI3 as the light-absorbing layer for its high repeatability.Based on the device structure of ITO/PEDOT:PSS/FASnI3/C60/BCP/Ag,we fabricate device to explore the basic preparation process of FASnI3 PSCs.The main works are focused on researching the effects of the devices with different solvent volume ratio concentrations(DMF and DMSO)and different SnI2 molar ratio concentrations.The optimized results show that the device prepared with the precursor solvent DMF:DMSO volume ratio of 4:1,SaI2:FAImolar ratio of 1.1:1 has the best performance The best device has a PCE of 5.87%,and the open circuit voltage(VOC)rises to 0.483 VSecondly,we introduce a material named 1,6 hexamethylenediamine hydroiodide(HDADI)to passivate the FASnI3 PSCs.The decent PCE and long-term stability were associated with the interaction of NH3+ and SnI64-octahedra via hydrogen bond(N-H…I),which not only neutralized charged defects or dangling bonds of perovskites,but also formed a shield to retard the oxidation of Sn2+ to Sn4+and reduce Sn vacancies,resulting the high-quality perovskite films with large coverage,high crystallinity and disappeared pinholes as well as increased radiative recombination and prolonged carrier lifetime.By optimizing the doping concentration,the efficiency abd stability of the device have been greatly improved.The champion device has achieve 7.6%PCE,and the unencapsulated device exhibited outstanding long-term stability,which can retain 80%of its initial efficiency for over 550 hours storage in a glove box with N2 environmentFinally,we further find a material containing both amino groups and hydroxyl functional groupsnamed tris(hydroxymethyl)aminomethane(THAM),and apply it to FASn1I3 perovskite solar cells.A series of characterization results show that the additive also has significant effects on the regulation,crystallinity,and light absorption of the FASnI3 perovskite film.In addition,doping THAM can effectively passivate defects,reduce defect density,and adjust the energy level structure,thereby improving the open circuit voltage and short circuit current density of the device.By optimizing the doping concentration,the efficiency and stability of the device have been greatly improved.The best device has achieved 8.14%PCE,and the unencapsulated device retains 60%of its initial efficiency when exposed to air environment for 35 h. |
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