Preparation And Properties Of New Carrier Transport Materials Of Perovskite Solar Cells

In recent years,organic-inorganic hybrid perovskites are widely used in many fields such as solar cells,light-emitting diodes and photodetectors,which have excellent absorption coefficient,wide absorption range in visible light region,very high carrier mobility,bipolar carrier transport,adjustable band gap,simple processing,and low cost and many other excellent properties.Perovskite solar cells（PVSCs）,as an emerging photovoltaic technology,have been popular around the world in the past decade,and power conversion efficiency（PCE）has rapidly increased from the initial 3.8%to the current 24.2%ultra-high efficiency,but due to the low stability of devices,the high cost of some functional materials.The road of PVSCs to be commercialized is still far away.Therefore,this thesis mainly conducts related research on material synthesis and device structure.（1）The compact TiO₂ prepared by the traditional method needs to be annealed by air,and it is difficult to obtain a uniform film,which leads to a large series resistance of the corresponding device,a serious charge recombination,and a low filling factor,thereby affecting device efficiency.It is also difficult to obtain the high quality SnO₂ films due to the effect from air.Here,we use tetrabutyl titanate and stannous chloride dihydrate to form a homogeneous isopropanol solution,and use low temperature annealing to obtain highly uniform TiO₂@SnO₂ composite electron transport layers.The film morphology was improved and the charge recombination is also effectively suppressed.PCE of the device with a structure of ITO/ETL/Cs_0.05FA_0.81MA_0.14PbI_2.55Br_0.45/P3HT/MoO₃/Ag reach13.12%,which is higher than 11.23%of TiO₂ and 9.19%of SnO₂.（2）Benzodithiophenes（electron donors）with different side chains are copolymerized with isoindio（electron acceptor）for the achievement of two hole-transporting polymers.The photoelectric properties of these D-A-type polymer are changed by adjusting the side chain groups of BDT units,and their application potential on PVSCs is developed,which provides some valuable reference information for the design and synthesis of hole transport materials.Optimized PVSCs with non-doping HTL displayed PCE of 6.68%and 3.29%by using POBDTID and PSBDTID respectively.（3）Tetrachlorophthalimide is used as an electron-transporting material to replace the TiO₂ in a conventional planar perovskite solar cell（PVSC）.The device with the structure of ITO/ETL/Cs_0.05FA_0.81MA_0.14PbI_2.55Br_0.45/P3HT/MoO₃/Ag was fabricated.PCE of the device based on TCl-PDI electron transport layer was up to 14.73%,which was higher than 12.78%PCE of TiO₂ device,which is due to the larger and denser perovskite grains,more balanced carrier transport.At the same time,the stability of the device is greatly improved,and the initial efficiency can still be maintained at 90%of initial PCE after storage for 720 hours in the air environment after packaging.