| Metal halide based perovskites are emerged as one of the most promising candidates for photovoltaic applications due to their high carrier mobility,long carrier diffusion lengths,and suitable optical bandgaps.Furthermore,bebefiting from their extraordinary light emitting properties,there are extensive applications of these materials beyond photovoltaic,such as light-emitting diodes(LED),lasers,photodetector,and so on.Despite their outstanding optical performance,conventional three-dimensional(3D)organic-inorganic halide perovskites own terribly poor environmental stability,which significantly limits their commercialization.To date,studies on stability improvement of perovskites are under focus.Among them,introducing the structure of two-dimensional(2D)perovskites and fabricating all inorganic perovskites seem to be two effective solutions.However,the research of 2D perovskites is just in their infancy,and their PL mechanism are still under debate.On the other side,inorganic perovskites are mostly solution-preocessed nanocrystals,and they should store in suitable solvent to keep colloidal form.The strong ionic nature of perovskites limits the choice of solvent,which challenges the commercial application of these nanocrystals.Therefore,studies on both clarifying the PL mechanism of 2D perovskites and realizing solid storage of inorganic perovskites make sense in the stability enhancement of perovskite materials.In this thesis,we carried out the research on lead halide perovskites,and aimed to realize the stability enhancement of perovskite materials.For one thing,we performed comprehensive PL measurements on 2D perovskites to understand their PL mechanism,and investigated the effect of organic cation length on the exciton recombination of these materials.For another,we made new attempts on the synthesis of inorganic perovskites and realized their solid storage.The main contents in this thesis include:1.First of all,comprehensive photoluminescence(PL)studies are conducted on(C6H5C2H4NH3)2Pbl4(PEPI)organic-inorganic hybrid 2D perovskite crystals prepared through a layered solution method.Three kinds of excitonic emissions are identified as those of QD-like excitons,2D localized excitons,and self-trapped excitons,respectively.2.Effects of organic cation length on exciton recombination in 2D layered lead iodide hybrid perovskite crystals were carried out.A blue shift in PL as well as significantly enhanced internal quantum efficiency(IQE)is induced by the length increase in the phenylalkylammonium chains from PMA to PBA.Moreover,1D-like exciton recombination takes place in PBPI crystals,resulting from the structural rearrangement with enhanced length of organic ligands.To the best of our knowledge,this is the first time that organic cation length is discovered and elucidated that impacts the recombination dynamics of 2D perovskites.3.New attempts were made on the ultrathin fabrication of perovskites,and the optical properties of these products were investigated.Atomically thin 2D perovskite nanosheets were synthesized by liquid exfoliation.Single-and few-unit-cell-thick single-crystalline 2D hybrid perovskites were obtained in less polar solvents under mild ultrasonic condition.On the side,ultrathin PbI2 nanosheets were prepared by hot-casting,and eventually transferred to ultrathin CsPbI3 nanosheets through a chemical vapour deposition(CVD)process.The heating temperature was crucial to affect the morphology and thickness of 2D CsPbI3 nanosheets.4.Finally,full-inorganic perovskite nanocrystalline CsPbBr3 NCs was adsorbed into the hole of metal-organic framework(MOF)materials,and the CsPbBr3 NCs/uio-66 solids were produced.During the fabrication process,CsPbBr3 NCs was adsorbed into the hole of uio-66,nucleation and growth,and reached the maximum size under 160 ℃.Such CsPbBr3 NCs/uio-66 solids exhibit better stability than CsPbBr3 NCs stored in hexane,and thus may represent a pathway for their solid storage. |
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