Study On The Interface Modification Of Organic Solar Cells And Organic-inorganic Hybrid Perovskite Solar Cells

Recently,nanomaterials with unique chemical,electric and optical properties have been wildly used as the interfacial layer for novel optoelectronic devices.This dissertation is focused on the low-temperature and wet-chemical synthesis of n-type ligand-free rutile and anatase TiO2 nanocrystals,and p-type ultrathin two-dimensional(PEA)2PbX4(X=Cl,Br,I)nanosheets(NSs).The synthesized nanomaterials could serve as the interfacial layer for high-performance organic solar cell and organic-inorganic hybrid perovskite solar cells,meanwhile,the effect of interfacial materials on the performance of devices was investigated.Several aspects,including design,synthesis and physicochemical properties of nanomaterials,fabrication of interfacial layers,design and preparation of device with novel structure were studied and discussed,which may pave new way to design new nanomaterials for improvement of the device performance.(1)Ligand-free rutile and anatase TiO2 nanocrystals have been synthesized through a hydrolytic sol-gel reaction with water-bath method.These two kinds of TiO2 nanocrystals could be served as electron extraction layers for improving the performance in inverted polymer solar cells based on PTB7:PC71BM as active layer.Compared with the device fabricated by using amorphous TiO2(6.11%)and rutile TiO2(6.93%),the device based on anatase TiO2 shows a significant enhancement in power conversion efficiency(7.85%).The characterization of the interfacial layer and corresponding investigation of device property demonstrated that the improved performance of devices could be attribute to the TiO2 nanomaterials with uniform size,well-crystallization,good dispersity,and well-aligned band position.Moreover,the high quality interfacial layer based on TiO2 nanomaterials would decrease the election-hole recombination and enhance the electron extraction.(2)The free-standing phenylethylammonium lead halide perovskite(i.e.(PEA)2PbX4(PEA=C8H9NH3,X=Cl,Br,I))NSs with few-layer thickness were synthesized by using a facile antisolvent method.The as-prepared(PEA)2PbX4 NSs with controllable thickness could be well-dispersed in organic solvent.Meanwhile,the bandgap can be adjusted by exchanging halide ion.As a result,the absorbance and photoluminescence of(PEA)2PbX4 NSs in toluene changed from green to blue and finally to violet.By incorporating the(PEA)2PbX4 NSs into poly(3-hexylthiophene)(P3HT),the(PEA)2PbX4 NSs:P3HT composite films were fabricated as channel layers for the field effect transistors(FETs).All the resulting FETs show promising hole transport and current saturation behaviour at room temperature.Notably,the FETs based on(PEA)2Pbl4 NSs:P3HT exhibit the best hole mobility ?h of 1.43×10-1 cm2 V-1 s-1.(3)By using the synthesized ultrathin two-dimensional(PEA)2PbX4(X=Cl,Br,I)NSs as hole extraction layer and the obtained anatase TiO2 nanocrystals as electron extraction layer,we fabricated organic-inorganic hybrid perovskite(MAPbl3)solar cells through one-step method.Compared with the reference device(15.4%),the device based on(PEA)2Pbl4 NSs shows a significant enhancement(-20%)in power conversion efficiency(18.53%).We characterized the morphology,crystal structure,elemental composition,band structure and spectrum of the fabricated films.The performance improvement of the devices based on(PEA)2Pbl4 NSs can be attributed to the following reasons:1)the absorption efficiency of the composite films could be improved by incorporating the(PEA)2PbX4 NSs;2)the proper band position(PEA)2Pbl4 NSs would erase the defects of MAPbl3 film;3)the(PEA)2Pbl4 NSs with high carrier mobility can significantly enhance hole transfer.