Study On Sulfide Nanomaterials Applying For Organic Solar Cells

With the continuous progress and development of society,increasing energy demand and environmental pollution problems have become the focus of humanity.In order to address the problems caused by energy shortage and achieve sustainable development,it is necessary to reduce the use of fossil energy and develop cleaner and renewable energy.The unique advantages of relatively uniform distribution,wide range,and no pollution make solar energy widely available.In recent years,organic solar cells and organic-inorganic hybrid solar cells have been developed vigorously because they are more in line with the concept of green,low-cost,and high-efficiency development.Compared with other types of solar cells,organic solar cells have attracted considerable attention mainly due to the advantages of low-cost preparation,environmental friendliness,etc.However,the problem of low carrier mobility,easy charge recombination,and bad stability makes it unable to meet commercial applications.In particular,metal sulfide nanomaterials are one of the most essential members since they can serve as a promising candidate for photovoltaic converters due to its large absorption in the visible light region,excellent energy level matching with active layers and conductive substrate,large carrier mobility,and stability in water and air.The inorganic nanomaterials used in organic solar cells are expected to solve the problems of low carrier mobility,easy charge recombination,and poor stability.Inorganic-organic hybrid solar cells further avoid the problems of organic solar cells.At present,the conventional method for preparing inorganic-organic hybrid solar cells must use cosolvents and surfactants,which inhibit charge transfer between the acceptor materials and donor materials.In this work,the method of thermal decomposition of metal xanthate to prepare metal sulfide nanomaterials can effectively solve this problem.The method is easy to synthesise.In this respect,metal xanthate precursors are highly soluble in a variety of organic solvents,such as chloroform and chlorobenzene.A second beneficial,property of metal xanthates in this regard is that they decompose at low temperatures and the side products of the decomposition are volatile,which leads to tidy layers without impurities and the crystal grain size is small.In this work,the improvement of the efficiency of organic solar cells is mainly achieved by the modification of the electron transport layer,the doping of the electron transport layer and the doping of the organic active layer by the metal sulfide prepared by the thermal decomposition of thermal decomposition of metal xanthate.Bismuth sulfide prepared by the thermal decomposition of metal xanthate is used as the modification of zinc oxide as the electron transport layer.The bismuth xanthate complex was synthesized,and the structure,decomposition temperature and decomposition products were explored.Then,Bi₂S₃ was grown on the surface of ZnO by the thermal decomposition of bismuth xanthate to prepare solar cells with device structures of ITO/ZnO/Bi₂S₃/PM6:Y6/MoO₃/Ag.The effect of different thicknesses of Bi₂S₃ on device efficiency was explored The results shown that the efficiency of the cells using ZnO/Bi₂S₃ 6K（Bi₂S₃ rotation speed is 6000 rpm）double ETL is slightly higher than the device efficiency of the cells using only ZnO as the ETL under other conditions,and finally the best efficiency of12.50%was obtained.Interestingly,the device using ZnO/Bi₂S₃ 6K double ETL has better stability in the air than that using pure interface ZnO as ETL.Zn_xCd_1-xS films were prepared by the thermal decomposition of metal xanthate,and interface doping was used to improve device performance.The structures of the synthesized zinc xanthate complex(Zn（S₂COBu）₂ and cadmium xanthate complex（Cd（S₂COEt）₂（C₅H₄N）₂）were characterized,The decomposition temperature of xanthate complexes were further explored,the conclusion indicated that the good crystalline Zn_xCd_1-xS solid solution can be formed after annealing at 350℃.The UV–vis and band gap spectra indicate that the optical properties and band gap of the obtained Zn_xCd_1-xS solid solution can be continuously modulated by tuning their compositions.As a consequence,the solar cells with device structure of FTO/Zn_xCd_1-xS/P3HT:PC₆₁BM/MoO₃/Ag were prepared using Zn_xCd_1-xS films as the electron transport layers.The results shown that Zn_0.3Cd_0.7S as the electron transport layer has relatively excellent efficiency.Bismuth sulfide prepared by the thermal decomposition of metal xanthate is doped in the organic active layer to improve the performance of the device.Bi₂S₃ was grown in situ in the active layer PM6:Y6,as well as the conventional device with configuration of ITO/PEDOT:PSS/PM6:Y6:x%Bi₂S₃/PDINO/Al and the inverted device with ITO/ZnO/PM6:Y6:x%Bi₂S₃/MoO₃/Ag were fabricated.The results demonstrated that when a certain amount of Bi₂S₃ was doped into the active layer PM6:Y6,the efficiency of doped device is significantly higher than that of the undoped device.After that,the effect of doping different proportions of Bi₂S₃ in the active layer was explored in details.The conventional device and the inverted device were obtained the best efficiency of 12.87%and 13.53% respectively.