Research On The Photovoltaic Performance Of Novel Methylhydrazine-Based Two-Dimensional Perovskite Solar Cells

Solar cells are expected to solve the energy crisis,because it can directly convert solar energy into electric energy,and the entire process is environmentally friendly and pollution-free.The efficiency of perovskite solar cells has increased from the original 3.8% to 25.2% in just a few years,showing great application potential,but the lead toxicity and instability of perovskite still limit its commercialization.Therefore,this article first explored the effects of different structures and preparation methods on the efficiency and stability of perovskite solar cells.Then,a novel of methylhydrazine?MHz?₂D perovskite device was prepared and compared with FAPbI₃ and EAPbI₃ perovskite devices.Finally,three methods were used to introduce MHz cation into perovskite devices,hoping to improve the efficiency of MHz perovskite devices.The details are as follows.First,we investigated the effects of three fabrication processes on the performance of perovskite devices.Among them,the one-step planar structure device uses low-temperature annealed SnO₂ as the electron transport layer,which can save costs,and has high light transmittance and fill factor,so it has achieved a maximum efficiency of 18.8%.In addition,the one-step mesoporous structure device uses compact TiO₂ and mesoporous TiO₂ as the electron transport layer.Although the device has a low fill factor and short circuit current density,the mesoporous structure substrate enables the device to obtain an open circuit voltage of 1.14 V and excellent stability.Therefore,it has achieved a maximum efficiency of 18.3%.Finally,the planar structure device prepared by the two-step spin-coating method has the advantages of high crystallinity,large crystal grains,thicker film,and excessive PbI₂ passivation,so that the device current density was increased to 24.5 m A/cm².Therefore,it achieved a maximum efficiency of 20.9%.Second,this paper studied the effect of MHz as the perovskite A-site cation on device performance and compared it with two other similar molecules,FA and EA.The study found that although the molecular structures of EA,MHz,and FA are similar,1D,2D,and 3D perovskites are formed due to different ionic radius.Therefore,the band gaps of perovskite are very different,which are 2.42,2.17,and1.53 e V,respectively.Moreover,the efficiencies of the three perovskite devices are0.84,0.63,and 15.9%,respectively.In the experiment,we also found that the solvent has a significant effect on the MHz perovskite.After comparing DMF,DMSO and GBL solvents,we conclude that GBL is the most suitable solvent.Therefore,subsequent experiments used GBL solvent to dissolve the MHz perovskite.Third,in order to solve the problem of low efficiency of pure 2D perovskite,we have introduced MHz into perovskite in different ways,hoping to improve the efficiency of the device.First,we introduced MHz I as a dopant and surface passivator into Cs_0.05(FA_0.83MA_0.17)_0.95Pb(I_0.83Br_0.17)₃ perovskites,but the 2D MHz perovskites severely hindered carrier transport.Therefore,efficiency decreases as the amount of MHz I used increases.Then we prepared MHz quasi-2D perovskites with different layers.The introduction of MA reduces the band gap of perovskite,and the small n-phase in the quasi-2D perovskite film is vertically embedded in the sizeable n-phase perovskite,which improves the carrier transport capacity.Therefore,an efficiency of5.83% was obtained when n = 4,and the repeatability and stability of the device is also excellent.