The Ligand Modification Of CsPbBr₃ Quantum Dots And Synthesis Of Tunable Luminescent CsPb₂Br₅ Nanoplatelets And Their Applications

Recently,inorganicperovskiteandperovskite-relatedsemiconductors nanomaterials have been developed rapidly and present potential applications in solar cells,light-emitting diodes,photodetectors and micro-lasers,due to the advantages of less defects,long carrier diffusion,bandgap tunable,high-effective emission and solution process.However,inorganic perovskite CsPbBr₃ nanoparticles are easily aggregated,and perovskite-related CsPb₂Br₅ nanoplatelets?NPLs?are difficult to control luminescence.In terms of these questions,we carried out ligand modification of CsPbBr₃ quantum dots?QDs?and synthesis of tunable luminescent CsPb₂Br₅ NPLs and their optoelectronic applications.The innovation points and main research results of this dissertation are summarizedas follows:?1?In order to solve the problem of easy aggregation of conventional oleic acid?OA?ligand CsPbBr₃ QDs,2-hexyldecanoic acid?DA?with one of the branched organic acids was proposed instead of OA,which can reduce the ligand carbon chain and increase the existence space of ligands.The synthesis of perovskite CsPbBr₃ QDs using DA was studied.The crystal structure,morphology,and optical properties of the synthesized materials were characterized.The results show that DA can successfully synthesize CsPbBr₃ QDs instead of OA.Through regular testing of photoluminescence spectra,photoluminescence quantum yield of two kinds of QDs,we found that the stability of DA-CsPbBr₃ QDs solution is better than OA-CsPbBr₃ QDs solution.Meantime,electroluminescent devices based on CsPbBr₃ QDs were prepared and analyzed.The DA-CsPbBr₃ QDs light-emitting diodes were found to be superior.?2?CsPb₂Br₅ NPLs of different sizes were synthesized by hot-injection method.The composition,structure,morphology,and optical properties of the material were analyzed.The results show that by adjusting the temperature,we synthesized three different color NPLs,blue,cyan and green.With increasing the temperature,the absorption and emission peaks present a progressive red-shifted,the average grain size decreased from 1?m to 200 nm,the thickness of NPLs increased from 10 nm to 20 nm.?3?In order to study the electrical and optical properties of CsPb₂Br₅ NPLs,the preparation and analysis of photoluminescent devices and photodetectors are carried out.The CsPb₂Br₅ NPLs synthesized at 140°C can emit narrow-band green light,which is expected to be used as a green phosphor to construct green light-emitting diodes.Therefore,we used GaN-based blue light-emitting diodes chips and CsPb₂Br₅ NPLs to study the fluorescence-converted green light-emitting diodes.We studied the relationship between the amount of CsPb₂Br₅ NPLs and the green-light fluorescence conversion,and analyzed the mechanism of the reduction in the luminous efficiency of green light-emitting diodes.We successfully constructured pure green fluorescent conversion light-emitting diodes based on perovskite-related CsPb₂Br₅ NPLs.Photodetectors based on CsPb₂Br₅ NPLs synthesized at different temperatures were prepared.After comparison,the NPLs synthesized at 100°C had the best photoelectric response.The photocurrent switching ratio was 364%,the photoresponsivity was 340?A/W and the rise and fall times were 0.426 s and 0.422 s,respectively.In summary,perovskite CsPbBr₃ QDs and perovskite-related CsPb₂Br₅ NPLs have characteristics such as adjustable bandgap range,high luminous efficiency,large emission wavelength coverage,and good optical stability,this has guiding significance for further study of the application of perovskite semiconductor nanomaterials.