| Polycrystalline ABX3 perovskite materials have shown great potential in the field of electroluminescent devices(LEDs),due to their advantages of high color purity,tunable bandgap,high carrier mobility,low exciton binding energy and solution processing.Future optoelectronic products with ultra-high definition,integrated displays,flexible wearability,and green environmental innovation will be on the rise thanks to the 5G smart era.In the process of PeLEDs,the research and optimization about the bottleneck problems such as crystal stability,high photoelectric efficiency and flexible large-area preparation are of great practical importance.Among them,the creation of high-quality emitting films with a uniform,pore-free surface is the primary challenge to achieving high-efficiency PeLEDs.And the selection of functional layer materials,preparation process optimization and energy level matching are the key ways to optimize the device structure.Therefore,perovskite nucleation and crystal growth were controlled using additive engineering and substrate optimisation to passivate surface flaws and enhance film formation.To address the balance of electron and hole transport,the formulation and preparation process of functional layers were optimized by interface engineering regulation to quench excitons and realize the printed preparation of all-solution-processed PeLEDs in ambient air.The main research contents are summarized as follows:1)Based on PeLEDs structure,the duration of oxygen plasma treatment of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)(PEDOT:PSS)film substrate is optimized to provide hydrophilic surface properties,matched work function,flat film morphology and good hole mobility,which is more favorable for the uniform growth of the underlayer of light emission.The optimal treatment time of 4 min was chosen to improve the coverage,crystallinity,uniformity,fluorescence performance and decay lifetime of CH3NH3PbBr3 film.In substrate regulation of perovskite film formation,oxygen plasma treatment formed nanoislands in the PEDOT:PSS films,providing more nucleation sites and improving the performance of all solution processed PeLEDs.The highest luminance of the device prepared with underlayer oxygen plasma treatment was 237.4 cd m-2,which was 2.19 times higher than that of the device without treatment(74.3 cd m-2).2)Synergistic mechanism of polyethylene oxide(PEO)and 1,3,5-tris(1phenyl-1 H-benzoimidazol-2-yl)benzene(TPBi)doping for surface defects in perovskite nucleation and crystal growth.Discussion on the enhancement effect of PEO in restricting grain size,filling grain gap and TPBi in passivating defects and increasing grain quality.The TPBi doping ratio was further investigated by comparing the morphology,crystallization optical properties and lifetime properties of films.The doping ratio of TPBi was CH3NH3PbBr3-PEOTPBi=1:0.05:0.025 so that the grain boundaries of films could be passivated effectively by proper amount of passivator.The brightness of device with doubleadditives was improved by 8.43 times compared with that of the undoped device,which showed the synergistic advantage of double-additives had a distinctive impact on the performance of PeLEDs in ambient air.3)In order to fabricate all solution processed PeLEDs with ordered energy level arrangement of each functional layer in air,PEDOT:PSS was treated with different alcohols to enhance the hydrophilicity of hole transport layer,optimize energy level structure and improve film-forming.By lowering the Coulomb force and altering the backbone structure,methanol-treated PEDOT:PSS films were chosen to increase their conductivity,carrier concentration,and mobility.This improved the hole injection ability and decreased the turn-on voltage to 2.5 V in PeLEDs devices.The electron transport layer TPBi concentration of 20 mg mL-1 was optimised based on the multilayered PeLEDs structure to improve the electron-hole transport balance to improve the exciton radiative recombination.The effect of different Ag materials and thickness on the photoelectric characteristics of the device was investigated by using the scrape-coated preparation solution top cathode instead of vacuum evaporation method. |
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