Effects Of Urea Addition On Microstructure And Photoelectric Properties Of Perovskite Films

Organic-inorganic hybrid perovskite solar cells are favored by researchers for their low cost and excellent photovoltaic performance.In the structure of a perovskite solar cell,the quality of the perovskite light absorption layer is the key to determine the energy conversion efficiency of the solar cell.Large-grained perovskites can suppress the recombination of carriers in the grain boundary,extend the life of carriers,and enhance the mobility of carriers.In the planar structure perovskite battery,having a dense,flat,high crystallinity perovskite active layer is one of the necessary conditions for obtaining a solar cell with high photoelectric conversion efficiency.Introducing additives into the perovskite precursor solution and regulating the perovskite morphology by regulating the interaction between the perovskite and the matrix is one of the most widely used methods to optimize the perovskite film.In this paper,urea is used as an additive to regulate the crystallization process of perovskite by regulating the interaction between urea and the perovskite matrix.The effect of urea addition on the microstructure and photoelectric properties of perovskite films is studied.The addition of Lewis base in the perovskite helps to form a dense,smooth,pinhole-free,and passivated defect perovskite film.The paper first selected the typical urea and thiourea in the Lewis base as additives to study its calcium Titanium thin film microstructure and its influence on photoelectric performance.Add 5%urea and thiourea to the perovskite precursor solution to prepare perovskite film and assemble the battery.Through the characterization of the morphology and structure and battery performance test,it was found that both urea and thiourea can increase the calcium and titanium The crystallinity of the ore film,but the film prepared by adding urea to the perovskite precursor solution has better compactness and flatness,and has a more obvious effect on improving the photoelectric conversion efficiency of the battery.Therefore,urea is selected as the following chapter The additives of the perovskite precursor solution were further studied in detail.In the case of selecting urea as a perovskite precursor additive,the effect of different urea additive concentrations in the perovskite precursor solution on the microstructure of the perovskite thin film prepared by the one-step method and the photovoltaic performance of the assembled battery were studied in detail.Through the characterization of the morphology and structure of the perovskite film and the battery performance test,it was found that the perovskite film prepared by adding 10%concentration of urea has high crystallinity,large grain size,and strong light absorption capacity.The highest is 18.31%.The mechanism of action of urea was studied by Fourier infrared（FTIR）.After the addition of urea,MAI·Pb I₂·DMSO·urea intermediates will be formed in the perovskite precursor solution,which can increase the crystalline quality of perovskite and increase the grain size by delaying the crystallization rate of perovskite.On the basis of optimizing the content of urea additives in the precursor liquid,further adding urea into the two-step process to prepare the mixed FAPb I₃ perovskite film,by optimizing the content of the additive,a large-grain perovskite film was obtained,and the battery performance Significantly improved.The effect of adding urea to the Pb I₂ precursor solution on the microstructure and photoelectric properties of the perovskite thin film prepared by the two-step spin coating method was studied in detail.Through the characterization of the morphology and structure of Pb I₂ films and perovskite films prepared by adding different concentrations of urea in Pb I₂ precursor solution and the battery performance test,it was found that perovskite films prepared by adding 5%concentration of urea has high crystallinity an,large grain size and strong light absorption ability,and the photoelectric conversion efficiency of assembed batteries was the highest,up to 20.62%.Fourier infrared（FTIR）spectroscopy showed that urea coordinated with Pb I₂ to form a Pb I₂·O=C（NH₂）₂ intermediate,and a larger-sized Pb I₂ flake was formed by delaying the crystallization rate of Pb I₂.Larger Pb I₂ flakes with fewer nucleation sites facilitate the formation of perovskite with larger sized grains.The steady-state photoluminescence（PL）and time-resolved photoluminescence（TRPL）of the perovskite film also show that the addition of urea can effectively suppress non-radiative decay,reduce film surface defects,accelerate the electron transmission process and improve the electron extraction rate.Make the short circuit current density(J_sc)and fill factor（FF）significantly improved,thereby obtaining higher photoelectric conversion efficiency.Urea addition can not only improve the photoelectric conversion efficiency of perovskite batteries,but also improve its stability.This may be because the perovskite film prepared by adding urea is relatively dense and flat,and the interface contact between the perovskite layer and the hole transport layer is optimized,which indirectly reduces the contact between the perovskite layer and the air,thereby improving the stability of the perovskite battery.