| In recent years,the successful application of organic-inorganic metal halide perovskites in photovoltaic devices has attracted wide attention from researchers,while the all-inorganic lead halide cesium perovskite CsPbX3(X=Cl,Br,I)quantum dots(PQDs)are currently widely used in photovoltaic devices such as solar cells,lasers,and light-emitting diodes due to high luminescence quantum yield,narrow emission spectrum,adjustable emission spectrum and higher stability.However,the CsPbX3(X=Cl,Br,I)PQDs have weak intrinsic structural stability and low environmental resistance to water,light and heat.It is prone to fluorescence quenching,which hinders the further application and development.In this paper,a simple and effective anti-solvent method is used to synthesize CsmMA0.4-mPbBr3 and CsPbX3(X=Br,Cl/Br)PQDs.Styrene(PS)polymer form composite films or microspheres(MSs),which further improves the air stability and photostability of PQDs.The research content and results of the thesis are summarized as follows:Using anti-solvent method,DMF is used as a benign solvent to dissolve cesium bromide(CsBr)and lead bromide(PbBr2).CTAB is a surface ligand,anhydrous toluene is acted as a poor solvent to synthesize a series of CsmMA0.4-mPbBr3(m=0,0.1,0.2,0.3,0.4)PQDs at room temperature.It is found that the as-prepared PQDs have a cubic phase structure by structural and optical performance analysis.When m increases from 0.1 to 0.3,the size of the PQDs decreases from 18 nm to 10 nm,and then,the PL emission peak exhibit a blue shift.The morphology of MAPbBr3 with m=0 is nanosheet.When m=0.2,PQDs have a strongest emission and air stability,which the PL intensity only decays to 36.6%in 5 days.Three kinds of alkyl ammonium bromide with different chain lengths such as DTAB,CTAB and STAB are used as surface ligands.The as-obtained CsPbBr3 PQDs with different chain lengths have a cubic perovskite crystal structure.The average diameter of DTAB,CTAB,and STAB-CsPbBr3 are 10.5 nm,11.9 nm,and 13.9 nm,corresponding PL emission peaks are located at 512 nm,513 nm,and 514 nm,respectively.The PL intensity increases first and then decrease after reaching a highest intensity for CTAB-CsPbBr3.From this,CTAB was determined to be the best ligand,the optimal dosage was 0.04 mmol.Further,the CsPbBr1.5Cl1.5 PQDs with bright blue emission was synthesized by partial Cl-substitution,corresponding PL emission peak was blue shifted from 513 nm to 470 nm.A comparative study of OLA-CsPbBr3 and CTAB-CsPbBr3 synthesized by anti-solvent method.It showed that the as-synthesized CTAB-CsPbBr3 PQDs had a slower drop about 22.4%in PL intensity within 10 days,and lost 73.3%under UV light for 5 hours.The air stability and photostability are higher than those of OLA-CsPbBr3 PQDs.The mechanism research shows that CTAB has a larger steric hindrance,which is distributed around the octahedral PbBr64-to form a protective layer.CTAB can prevent the aggregation of PQDs to some extent.In CTAB,Br-acts as an additional bromine source donator,which can reduce the formation of VBr(bromine defect)and generate more structurally perfect PbBr64-octahedrons.The green emission CTAB-CsPbBr3@PS film and the blue emission CTAB-CsPbBr1.5Cl1.5@PS film were prepared by the solvent thermal evaporation method,corresponding component@PS MSs were prepared by electrospraying.In comparison of PL emission spectra,the optimal loading of CTAB-CsPbBr3 is 10 wt%in the polymer film.In comparison of SEM images,the best spinning conditions for polymer MSs are obtained:polymer concentration:15%;flow rate:20 μl min-1;injection distance:25 cm.CLSM(Confocal laser scanning microscope)results show that CsPbX3(X=Br,Cl/Br)@PS MSs are dispersed in the PS matrix with an average size of～10 μm.By comparison,it is found that CsPbX3(X=Br,Cl/Br)@PS MSs have better air and photostability than pure CsPbX3(X=Br,Cl/Br)PQDs solution or PS film.After storing in air environment for 10 days or UV light irradiation for 5 hours,the PL maximum intensity of CsPbX3(X=Br,Cl/Br)@PS MSs have not obvious change in comparison with CsPbX3(X=Br,Cl/Br)@PS film. |
PDF Full Text Request