Preparation And Performance Analysis Of Thiophene-based Two-dimensional Perovskite Crystals

Organic-inorganic hybrid perovskite,as a semiconductor material with excellent properties,has the advantages of high carrier mobility,high absorption coefficient,long carrier life and adjustable band gap.In the current research,Perovskite hydrolyzes easily in the air,improving the environment stability of perovskite solar cells has become a topic often discussed.Generally,adding additives or reducing defects on the surface of the perovskite film can improve the enviroment stability of the perovskite in the air.When a suitable organic amine cation is introduced,the three-dimensional structure of the perovskite is cut into a layered two-dimensional perovskite structure.Among,the excellent characteristics of the two-dimensional Ruddlesden-Popper(RP)structure,such as large variability and ease of processing,have been extensively studied.The chemical formula of RPP two-dimensional perovskite is L2An-1BnX3n+1,where L is a large organic cation.However,due to the large difference in the dielectric constant between the organic cation and inorganic perovskite layers in the two-dimensional perovskite,a unique quantum well limiting effect is formed.The RP perovskite solar cell has low photoelectric conversion efficiency.In order to overcome this shortcoming,the optimization of the molecular structure design of organic amine cations has become the key to improving the performance of RP two-dimensional perovskite solar energy.Summarizing from the current work,most of the studies focus on the research of n-butylamine(BA)and phenethylamine(PEA)as organic amine cations in two-dimensional perovskites,but the alkane chain of BA is generally hydrophobic,and as the aromatic ring structure of PEA has strong hydrophobicity,the steric hindrance of the benzene ring is relatively large,and the arrangement of the ?-? stack will further increase the layer spacing,reducing the charge transfer efficiency,resulting in low battery efficiency.According to the experimental results,it can be fully proved that using thiophene-based organic amines,the interlayer distance between two-dimensional perovskites is smaller than that of PEA-based two-dimensional perovskites.This property is more conducive to the transport of charge in the perovskite film;at the same time,because the thiophene organic amines have greater steric hindrance than the alkane chain,the stability of the perovskite film in the air is also huge.In summary,thiophene-based organic amines have achieved the enviroment stability of aromatic ring amines,and the layer spacing is smaller than that of benzene ring organic amines.Because thiophene ring and benzene ring is not the same,and thiophene ring according to the axial symmetry of S element,so-NH2 functional group substitution there is a 2 and 3 position difference.Therefore,we prepared 2-thiophene series of two-dimensional perovskites,including 2-thiophenmethylamine(2-TMA)and 2-thiophenethylamine(2-TEA).2-thiophene crystals were synthesized by the reaction of lead salt and organic amine under hydroiodic acid and rapid crystallization.A series of(2-TEA)2(MA)n-1PbnI3n+1(n=1,2,3)and(2-TMA)2(MA)n-1PbnI3n+1(n=1,2,3)were prepared and characterized by optimizing the ratio of raw materials and reaction conditions.In addition,experimental data show that 2-thiophenethylamine than phenylethylamine layer spacing is smaller,confirmed that thiophen-like RPP crystal has a more compact than benzene ring crystal stacking structure.Finally,(2-TEA)2(MA)2Pb3110 and(2-TMA)2(MA)2Pb3I10 crystal materials were selected as precursors to prepare two-dimensional perovskite films.The photoelectric conversion efficiency of the devices based on(2-TEA)2(MA)2Pb3I10 reached 11.92%,which was much higher than the 6.01%based on(2-TMA)2(MA)2Pb3I10.In addition,we selected 3-TMA and 3-TEA isomers for comparison and comparison.According to the previous experimental ideas,we preferentially prepared crystals with(3-TMA)2(MA)n-1PbnI3n+1(n=1,2,3),and(3-TEA)2(MA)n-1PbnI3n+1(n=1).According to XRD data,it is found that the interlayer distance of the 3 bit substitution is slightly larger than that of the 2 bit substitution.From the ultraviolet spectrum,we see that as the value of n increases,the band gap gradually decreases,and the crystals are also pure phases.At the same time,the efficiency based on(3-TMA)2(MA)2Pb3I10 device is 10.21%.