Energy,information,and materials are the three pillar industries of the 21st century,and the developments of novel semiconductor materials provide a foundation for the progress of energy and information.In recent years,halide perovskites have become a hotspot of research due to their superior optoelectrical properties.Especially,the halide perovskite nanocrystals have caused a wide public concern because of their unique quantum effect and low-cost synthesis process,holding great promise in many fields,such as light-emitting diode(LED),solar cell,photodetector(PD),and so on.However,there are still some unsolved problems in the study of halide perovskite nanocrystals.Firstly,the high-quality halide perovskite nanocrystals are usually prepared by a hot injection solution phase process.High temperature and inert gas protection are inevitable in hot injection,which cloud increase cost and limit output.Secondly,most halide perovskite nanocrystals are based on lead,and the toxicity of lead in perovskites severely limits their practical applications.In this dissertation,the halide perovskite nanocrystals are the main research focus,the modified room-temperature solution phase methods are proposed to synthesize high-quality halide perovskite nanocrystals,and their optoelectrical properties and the inner mechanisms are studied in depth.By means of material design,ligands modification and interface engineering,the performances of the perovskites-based optoelectronic devices are enhanced.Moreover,this dissertation also introduces the synthesis and properties of lead-free Bi-based perovskite nanocrystals,as well as their application on optoelectronic devices.The main contents of this dissertation include the following aspects:1.The chromaticity of halide perovskite nanocrystals are relatively unexplored but very crucial to applications.A facile ligand-assisted solution process was proposed to synthesize quasi-2D perovskite CsPbBr3 nanoplatelets(NPs)with ultrapure green photoluminescence(PL)at room temperature on a large scale.The CsPbBr3 NPs exhibit an emission peak at 526nm with a narrow FWHM of 16 nm.The CsPbBr3 NPs are used for backlighting and show a CIE coordinate at(0.145,0.793),which covers 91%of color gamut of Rec.2020 standard in the CIE 1931 color space.The value represents the“greenest”backlight among all-inorganic perovskites ever reported.The photoluminescence quantum yield(PLQY)of the CsPbBr3NPs is measured to be 87%,which is attributed to the high exciton binding energy(85.6 me V)of NPs.These quasi-2D CsPbBr3 NPs also exhibit an outstanding stability in the air,and a WLED was fabricated based on these CsPbBr3 NPs.2.Halide perovskite nanocrystal films with high crystallinity and thickness tunability are suitable to be assembled into high-performance PDs.Highly-crystalline CsPbBr3 nanosheets(NSs)with large size were synthesized via a modified solution template method and used for well-behaved PDs.The CsPbBr3NSs have a lateral size of 5μm and a thickness of 17 nm.Semiconducting polymer PCBM is incorporated as functional additive to improve the PD performance,PCBM forms heterojunction with CsPbBr3 NSs,which is conducive to extract and collect photogenerated charge carriers.Moreover,PCBM functions as film modifier help to improve the quality of the blending films,which boosts the effective transport of charge.The performances of hybrid CsPbBr3/PCBM PD show a huge advantage compared to the CsPbBr3 PD.The CsPbBr3/PCBM PD exhibits a high specific detectivity(3.06×1013 Jones),fast response time(rise:44μs,decay:0.39 ms)and a broad linear dynamic range(73 d B).Importantly,the CsPbBr3/PCBM film-based PD based on flexible polyethylene terephthalate(PET)substrate was fabricated,and the device exhibits an outstanding mechanical flexibility and a robust electrical stability.3.The toxicity of lead content severely limits the practical applications of lead halide perovskites.Via a facile solution process,newly low-toxicity Bi-based perovskite FA3Bi2Br9quantum dots(QDs)were prepared.By varying the precursor solutions,the emission peaks of the full series FA3Bi2X9(X=Cl,Br,and I)QDs could be tuned from 399 nm to 526 nm.The as-synthesized FA3Bi2Br9QDs exhibit a bright blue emission at 437 nm with a high PLQY of52%.The FA3Bi2Br9perovskite was demonstrated to have a direct bandgap(2.84 e V)by the density functional theory(DFT)calculations.As to the origins of high PLQY,the observed high exciton binding energy(274.6 me V)and low defect density are proposed to promote the exciton generation and the efficient radiative recombination.Besides,the FA3Bi2Br9 QDs show good air stability and ethanol stability.And a lead-free perovskite blue LED was fabricated successfully by combing FA3Bi2Br9QDs/PS composites with UV light chip.4.Through a facile solution process,hexagonal Cs3Bi2I9 single crystal NPs were prepared at room temperature.The as-prepared Cs3Bi2I9NPs are thin layer materials with a lateral size of 10μm and a thickness of 87 nm.The structure and morphology characterizations demonstrate the high crystallinity and good smoothness of the Cs3Bi2I9NPs.Both experimental results and computational calculations confirm the indirect(quasi-direct)bandgap nature of Cs3Bi2I9 perovskite.Basing on these Cs3Bi2I9 single crystal NPs,a photodiode PD with vertical structure was fabricated.In comparison to those planar PDs,the Cs3Bi2I9 NPs PD with vertical structure possess much shorter conductive channel,and thus it exhibits a superior photoresponse performance.The device shows a responsivity of 47.4m A/W at a bias voltage of 5 V,and a rise time of 0.86 ms and a fall time of 2.21 ms,respectively.In addition,the Cs3Bi2I9 PD can well maintain the initial performance after 3months of storage in the air. |