| In recent years,due to the excellent photoelectric properties and low-cost solution processing of organic-inorganic hybrid metal halide perovskite materials,they have been widely explored and applied to various semiconductor devices,such as solar cells.The highest power conversion efficiency(PCE)of perovskite solar cells(PSCs)has reached25.5%,indicating broad commercial application prospects.Among various kinds of PSCs,hole-conductor-free,printable mesoscopic perovskite solar cells(p-MPSCs)based on triple-layer structure of mesoporous titanium dioxide/mesoporous zirconium dioxide/carbon electrode have attracted widespread attention due to their unique advantages in low-cost,excellent long-term stability and large-scale fabrication.In this thesis,a series of studies,including optimizing energy level alignment in the device,optimizing the crystallization and composition of perovskite materials,have been conducted to improve the PCE of p-MPSCs,boosting p-MPSCs'highest PCE to 18.82%.The main contents are as follows:(1)Tuning the Fermi level of halide perovskites to optimize energy level alignment within the device via additives.The energy level alignment at the interface in p-MPSCs were optimized by introducing amide additives,including formamide,acetamide and urea,which were found to increase the work function of perovskite from 4.36 e V to 4.63 e V,4.65e V and 4.61 e V,respectively.Upon the addition of theses additives,the charge transfer between the perovskite and mesoporous titanium dioxide is promoted,and recombination in the perovskite film is inhibited.As a result,the PCE of p-MPSCs is increased from 14.26%to 15.57%.(2)Preparing high-quality MAPbI3 films without pre-synthesized MAI.N-methylformamide(NMF)was applied as solvent and methylamine source to react with hydroiodic acid(HI)to generate MAI through a hydrolysis reaction in the precursor,and then generating MAPbI3 by reacting with Pb I2 in the precursor for preparing p-MPSCs.The as-prepared MAPbI3 films exhibit better crystallinity,stronger light absorption ability and suppressed non-radiative recombination.By optimizing the hydrolysis and crystallization process,p-MPSCs deliver a highest PCE of 15.99%.(3)Growing highly oriented MAPbI3 film in the triple-layer through precursor design and crystallization process control.Highly dissolved precursor with few large colloidal particles was prepared by adopting NMF as solvent and MACl as additive.By carefully controlling the volatilization rate of solvent from the wet film,the crystallization process of MAPbI3 with fewer nucleation sites and sufficient growth is realized.Highly oriented MAPbI3 crystals were obtained in the triple mesoscopic layer by this method,and confirmed by grazing incidence wide-angle X-ray scattering(GIWAXS).The fabricated p-MPSCs achieved a highest PCE of 18.82%with an open circuit voltage(VOC)of 1025 m V,short-circuit current density(JSC)of 22.82 m A/cm2,and fill factor(FF)of 0.80.This is the highest value for p-MPSCs.Meanwhile,the devices also exhibit promising long-term operational stability by maintaining 95.7%of the initial PCE after 1000-hours continuous illumination under maximum power point(MPP)operating at 55±5°C and 92.4%of the initial PCE after1340-h thermal aging at 85°C/85%Humidity.(4)Developing efficient p-MPSCs based on formamidine/methylamine mixed-cation perovskites.The influence of FA amount in MA1-xFAxPbI3 on the phase and absorption spectrum of films,and performance of p-MPSCs was studied.When the ratio of FAI is 75%,the obtained film exhibits a red-shift absorption cut-off edge of 804 nm from 780 nm and exhibited better charge transport capacity and suppressed non-radiative recombination,and the corresponding p-MPSCs exhibited a highest PCE of 17.45%.At the same time,benefited from the developed crystallization control method based on the NMF solvent system,the formation of by-product of?-FAPbI3 in the film was reduced and did not affect the device performance significantly. |
PDF Full Text Request