FA_xMA_1-xPbI₃ Preparation,Characterization And Device

Organometal halide perovskite materials(Organometal halide perovskite materials)have unique properties,such as a band gap value of 1.55e V,strong absorption of light from visible light to near-infrared,and a high absorption coefficient(10⁴cm^-1)the above);It has high carrier mobility(about 800cm²V^-1s^-1),long carrier diffusion length(over 1?m),and has good transport characteristics for both electrons and holes.Therefore,organic metal halide perovskite materials have made great progress in the field of solar photovoltaic technology.At the same time,it has potential application prospects in optoelectronic devices such as perovskite light-emitting diodes,MOS field effect tubes,and memristors.This thesis focuses on the preparation and characterization of the mixed cationic FA_xMA_1-xPbI₃ perovskite film,and the research on the solar cells and memristors based on the FA_xMA_1-xPbI₃ perovskite film.The research methods and results are summarized as follows:Preparation and performance study of mixed cationic FA_xMA_1-xPbI₃ perovskite film:This paper uses a two-step solution method to prepare mixed cationic FA_xMA_1-xPbI₃(x=0,0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8,0.9)Perovskite film.The typical preparation process is as follows:In the first step,the PbI₂ powder is dissolved in a mixed solvent of DMF and DSMO to form a precursor solution with a concentration of 1.0M,and the PbI₂ film is prepared by spin coating technology.In the second step,the PbI₂ film is immersed in a solution with a concentration of0.063M.The solution uses IPA as a solvent and FAI and MAI as solutes.By changing the amount of FAI and MAI in the precursor solution,the FA⁺component x is at 0 change from to 1,the influence of FA⁺components on the structure,morphology and optical properties of FA_xMA_1-xPbI₃ was studied;At the same time,the influence of the immersion time of the PbI₂film on the morphology,structure and performance of the FA_0.4MA_0.6PbI₃ perovskite film was discussed.1.The two-step solution immersion method can well control the morphology and uniformity of the film,and has high repeatability and good controllability.With the gradual increase of the component x of FA⁺,the characteristic peak of XRD gradually shifts in the direction of low diffraction angle.This is because the size of FA⁺ion(0.279 nm)is larger than MA⁺ion(0.270 nm).When FA⁺replaces the position of MA⁺,the crystal increases.The size of the grid causes the XRD peaks to shift in the direction of low diffraction angles.At the same time,with the increase of the FA⁺ion content x,the absorption edge of FA_xMA_1-xPbI₃ and the PL peak continue to move to the long wave direction,which also proves the formation of the FA_xMA_1-xPbI₃ perovskite mixed film.This is because the band gap of FAPbI₃(1.43 e V)is smaller than the band gap of MAPbI₃(1.55 e V).When more FA⁺replaces the position of MA⁺,the band gap of the mixed cation FA_xMA_1-xPbI₃ perovskite hybrid film gradually becomes smaller.However,as the FA⁺ion content x in the film increases,non-photovoltaic active(?)-FAPbI₃ will be formed in the FA_xMA_1-xPbI₃ film.2.The morphology,structure and structure of the FA_0.4MA_0.6PbI₃ perovskite film formed after the PbI₂film is immersed in the same concentration(FAI+MAI/IPA)solution for 15min,20min,30min,and 35min,respectively,are studied.Optical performance,the results show:When the immersion time is 15min,PbI₂ does not completely transform the perovskite FA_xMA_1-xPbI₃ film;When the immersion time is longer than 20minutes,large square perovskite grains are formed on the surface of the perovskite FA_xMA_1-xPbI₃ thin film.When the immersion time is further extended to 30min or 35min,most of the small perovskite grains are corroded,resulting in low coverage of the perovskite film on the substrate.Research on the photovoltaic performance and stability of FA_xMA_1-xPbI₃ perovskite solar cells.Traditional PSCs are prepared in a glove box,and their structure is composed of conductive glass,electron transport layer,perovskite absorption layer,hole transport layer and metal counter electrode.Among them,the hole transport layer Au counter electrode has a high cost and solar cell stability is poor.In order to reduce the cost and improve the stability,in the air environment,the structure of FTO/dense Ti O₂/mesoporous Ti O₂/perovskite layer/C electrode without hole transport layer battery was prepared in this paper.The focus is on the influence of the composition of FA⁺ions in the mixed cationic FA_xMA_1-xPbI₃ absorber layer and the immersion time on the photovoltaic performance and stability of PSCs.1.With the increase of the composition of FA⁺ions in the mixed cationic FA_xMA_1-xPbI₃absorption layer,the short-circuit current density and photoelectric conversion efficiency of PSCs gradually increase first,and then gradually decrease after reaching the maximum.PSCs based on FA_0.4MA_0.6PbI₃ have the best photovoltaic performance.The short-circuit current density J_sc is 20.56 m A/cm²,the open circuit voltage V_oc is 0.82 V,the fill factor FF is 0.56,and the photoelectric conversion efficiency PCE is 8.91%.At the same time,after the battery was placed in the air for 1104 hours,the efficiency of the battery decayed to 67.5%of the original efficiency.2.The FA_0.4MA_0.6PbI₃ perovskite film formed after immersion in PbI₂ film for 15min,20min,30min,and 35min was used as the light absorption layer to prepare a set of PSCs.The results showed that:When the immersion time was extended from 15min to 35min,the short-circuit current density(J_sc)was significantly reduced from 20.56m A/cm² to 5.56m A/cm²,but the open circuit voltage(V_oc)and fill factor(FF)did not change significantly.Therefore,the average PCE decreased from 8.91%to 2.24%as the soaking reaction time increased.The significant reduction in J_sc and PCE may be due to the long soaking time and the poor coverage of the perovskite film.The two-step solution method was used to prepare perovskite films of(?)-FAPbI₃ and?-FAPbI₃ annealed at 80? and 170?,respectively.The memristive devices with structure of Ag/(?)-FAPbI₃/FTO and Ag/?-FAPbI₃/FTO were prepared.The research compares the electrical performance of these two types of memristors,and initially discusses the working mechanism of memristors.1.The memristor Ag/(?)-FAPbI₃/FTO has better memristive effect than Ag/?-FAPbI₃/FTO.Based on the(?)-FAPbI₃perovskitememristive device,as the number of positive voltage scans increases,the resistance gradually decreases,and as the number of negative voltage scans increases,the resistance gradually increases,and positive and negative voltage scans can change and restore the resistance of the device.2.The threshold voltage of the memristor based on(?)-FAPbI₃ is 0.4 V.In order to explore the working mechanism of the perovskite memristor,the structure of the C/FAPbI₃/FTO memristive device was prepared.Through the memristive effect based on the Ag electrode and the C electrode memristive device,it was found that the memristive characteristics are closely related to the electrode of the device.Relationship.The working mechanism of Ag/(?)-FAPbI₃/FTO memristor may be:when a positive voltage is applied,the silver wire will gradually become conductive,forming a low configuration.When a negative voltage is applied,due to Joule heating assisted dissolution,the conductive wire gradually becomes shorter and breaks,forming a high configuration.