Research On High-efficiency And High-stability Tin-based Perovskite Solar Cells Fabricated Based On Blade-coating

In recent years,the excellent photoelectric properties,solution processing,and low cost of perovskite solar cells have triggered a research boom and rapid development.Currently,the certified efficiency of perovskite solar cells has reached 26%,which is comparable to commercial silicon-based solar cells.Nonetheless,the utilization of traditional perovskite solar cells,which incorporate lead,presents noteworthy risks to both human health and the natural ecosystem,constituting a critical concern that necessitates resolution prior to its widespread commercial implementation.As a group element of lead,tin has a similar ion radius and similar electron cloud structure to lead ions.Tin-based perovskite materials also exhibit excellent semiconductor properties and an ideal band gap,making them currently recognized as the most promising lead-free perovskite solar cells materials.However,due to the lack of Lanthanide contraction,Sn²⁺is very easy oxidize to Sn⁴⁺,which significantly impacts on the efficiency and stability of tin-based perovskite devices.Additionally,the uncontrollable crystallization process of tin-based perovskites poses a huge challenge to the large-area fabrication of high-quality thin films.The current fabrication of tin-based perovskite thin films mainly relies on the laboratory-scale spin-coating process,and there are no reports of high-efficiency tin-based perovskite solar cells fabricated using compatible large-scale production coating processes.To address these issues,this study focuses on the lead-free perovskite material of PEA_0.1FA_0.9Sn I₃（PEA:phenethylamine and FA:formamidine）composition,through the regulation of crystallization kinetics,combined with solvent engineering,additive engineering,interface engineering,fabrication of organic-perovskite integrated devices,to achieve high efficiency and stable tin-based perovskite solar cell fabricated by blade coating process.The specific content includes:1.A perovskite solution based on dimethoxy ethanol with a low boiling point and non-toxicity was used to prepare tin-based perovskite solar cells,with an inverted tin-perovskite device（hole transport layer/perovskite/electron transport layer,p-i-n）,using PEA_0.1FA_0.9Sn I₃ as component.To adjust the nucleation and crystal growth rates of the perovskite,dimethyl sulfoxide（DMSO）was added to the precursor solution to counteract the high Lewis acidity of Sn²⁺and reduce the affinity for organic cations.Our work revealed that DMSO forms a weak complex with Sn²⁺in the precursor,thereby weakening the activity of the outer electrons of Sn²⁺and reducing the crystallization rate of the tin-based perovskite.The addition successfully improved the crystalline quality of the perovskite film,significantly reducing the density of internal defect,and enhancing carrier transport efficiency and lifetime.Finally,after optimization,we successfully achieved a tin-based perovskite solar cell with a power conversion efficiency（PCE）of 13.04%,approaching reported efficiencies for spin-coated tin-based perovskite solar cells.2.The additive engineering strategy was utilized to enhance the performance and stability of tin-based perovskite solar cells by selecting benzyl hydrazine hydrochloride（BHC）,which exhibits mild anti-oxidation properties,as an additive.Our discovered that BHC effectively inhibits the oxidation of Sn²⁺in the precursor solution,and can be incorporated into the perovskite lattice during fabrication to protect Sn²⁺in thin films.The reduction product of benzyl hydrazine can also passivate perovskite defects,further improving the performance of tin-based perovskite.By adding BHC,the stability of the tin-based perovskite is enhanced,reducing internal defects,and increasing carrier transport efficiency.By incorporating BHC,we successfully got a tin-based perovskite solar cell fabrication by blade coating with a PCE of 13.89%.Furthermore,this device maintained 94%of its initial efficiency even after being stored in a N₂ environment for1500 hours.3.The melt blending crystallization method was applied to prepare an organic blend layer on top of the tin-based perovskite layer.The organic blend layer was successfully prepared on top of the tin-based perovskite layer,addressing the severe carrier recombination issue at the interface between the perovskite and organic mixed films caused by the unfavorable morphology of the organic blend film.,and enables the extension of the near-infrared absorption in tin-based perovskite solar cells.The melt blending crystallization technique proves to be an effective method for improving the morphology of the organic mixed layer in organic solar cells.It achieves molecular-level blending of the organic blend thin films,thereby enhancing the exciton dissociation efficiency in the films.Moreover,melt crystallization enhance the crystallinity of both donor and acceptor molecules,thereby enhancing the exciton transport and carrier extraction of the organic blend layer.The MBC can be widely applied in the large-area fabrication of organic solar cells with various components.By the melt blending crystallization,several high-efficiency organic solar cells were successfully fabricated,including PM6:IT-4F devices with an efficiency of 13.86%,PM6:Y6 devices with an efficiency of 16.16%,and PM6:BTP-BO-4F devices with an efficiency of 17.17%.These devices rank among the top in terms of efficiency in the large-area fabrication of OSCs with same compositions.Additionally,an organic mixed layer of PM6:BTP-e C9 composition was fabricated on tin-perovskite film using the melt crystallization method.The melt crystallized organic thin film expanded the near-infrared absorption of tin-based perovskite,and ultimately integrated devices achieved a PCE of 14.09%.