| Quantum Dot light-emitting Diodes(QLED)have attracted the attention of researchers in the field of optoelectronic devices due to their superior characteristics such as high luminance,quantum efficiency and stability.After decades of development,the scientific researchers have made great efforts in the innovation and modification of quantum dots and charge transport layer materials,as well as device physics,structure optimization and manufacturing technology,which has improved the problems of low efficiency and brightness,unbalanced carrier injection,interface defects and light loss in QLED devices,and greatly improved the performance of the devices.It has laid a foundation for QLED technology to be gradually commercialized and even become the next generation of mainstream display technology.Although many difficulties have been overcome,the performance of QLED devices still needs to be further improved to reach application level.Electrons and holes in the QLED devices form excitons in the light-emitting layer of quantum dots and generate photons in the way of radiation recombination.The enhanced local electromagnetic field generated by local surface plasmon resonance effect(LSPR)can promote the resonant coupling between excitons and surface plasmon,which can effectively improve the radiation recombination rate and enhance the efficiency of devices.Plasmomic Gold Nanoparticles(Au NPs)have significant LSPR properties and are ideal nanomaterials for improving the performance of QLED devices.In this paper,Au NPs with specific LSPR absorption peak are synthesized by the phase transfer method.Moreover,due to the surface ligands of particles,there is a certain gap and self-assembly characteristics between particles,which makes Au NPs have a gap-plasma effect,showing a stronger local field.Based on this,we prepared Au NPs films and constructed a laminated TFB/Au NPs/TFB/QDs system to realize the LSPR near-field enhancement effect between Au NPs and QDs.Plasma micro-nano structure is an effective internal optical control measure.By introducing Au NPs film with micro-nano structure into QLED devices,the total internal reflection mode of the device can be broken,the light scattering can be enhanced,and the light trapped in each functional layer of QLED devices can be extracted.Based on the above contents,the main work of this paper is summarized into the following two parts:(1)Preparation and finite difference time domain simulation of oil-soluble spherical gold nanoparticlesFirstly,we synthesized oil-soluble spherical Au NPs with 6-7 nm particle size and good homogeneity and stability using toluene as solvent by phase transfer method,and its LSPR absorption peak was 515 nm.Then,Au NPs continuous films with low roughness and good film quality based on TFB film were prepared by spin coating method.When the concentration of Au NPs solution is adjusted from high to low,the micro-namo structure on the Au NPs film surface changes from island array structure to porous structure due to the self-assembly property of Au NPs and the volatile interaction of solvents.The prepared Au NPs films have LSPR absorption peaks at 470 nm and 530 nm respectively,which can match the luminescence peaks of blue and green QLED devices.Then,we use the finite difference time domain(FDTD)method to simulate the electromagnetic field intensity distribution around gold nanoparticles excited by light field.It is found that there is an obvious enhanced local field around a single Au NP;In the system composed of two or more Au NPs,the gap-plasma effect is produced between particles,and the local field is further enhanced.Finally,the near-field simulation and far-field simulation of the QLED devices based on Au NPs show that the near-field enhancement effect in the device is obvious,which is conducive to improve the radiation recombination rate of the QLED devices,and thus enhancing the luminescence performance of the device.(2)Construction and performance analysis of QLED devices based on plasmonic gold nanoparticlesBased on the above work,the Au NPs films with LSPR effect and micro-nano structure synergy are applied to construct green QLED devices to enhance the performance.In order to achieve effective near-field coupling between Au NPs and QDs,an interlayer is set to prevent the fluorescence quenching effect caused by direct contact between them.The QLED device structure is set as Glass/ITO/PEDOT:PSS/TFB/Au NPs/TFB QDs/Zn O/Al.After optimizing the thickness of interlayer and Au NPs layer,we studied the performance variation of QLED devices constructed with different concentrations of Au NPs solution.The experimental results show that the brightness and external quantum efficiency of QLED devices are improved obviously after Au NPs is added into the device.As the concentration of Au NPs solution decreases,the increase rate of external quantum efficiency decreases,while the increase rate of brightness increases.This is because with the decrease of concentration,the number of particles on Au NPs film decreases,resulting in the weakening of local field enhancement effect.Secondly,the change of micro-nano structure of Au NPs film from island shape to porous shape results in the increase of light extraction efficiency.When the dilution ratio of Au NPs solution is 1:6,the maximum external quantum efficiency is 25.87%,increasing by 69.5%,while the maximum brightness increase is only 3.9%.When the dilution ratio is 1:14,the maximum brightness is 177400 cd/m~2,increasing by 28.1%,while the maximum external quantum efficiency is only 34.7%.Finally,the blue QLED device based on Au NPs is constructed.,and its performance is also improved to a certain extent under the LSPR effect of Au NPs,... |
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