Study Of Luminescence Optimization Of OLEDs By Doping Of Nanomaterials

Organic light emitting diodes?OLEDs?have attracted numerous attention both in academic research and industry because of their advantages such as self-luminescence,low energy consumption,high resolution,full color and flexible,etc.It is regarded as the most promising candidate for the next generation of lighting and display technology.However,in the development of commercialization of OLEDs,they are still facing significant challenges in the efficiency optimization.The external quantum efficiency of OLEDs is mainly related to two factors:the internal quantum efficiency?IQE?and out-coupling efficiency.Among the optimization techniques,the approach by combination of localized surface plasmon resonance?LSPR?effect,light-scattering effect and/or magnetic effect,induced by the nanoparticles?NPs?,have attracted remarkable attention of researchers to improve the efficiency of OLED.In order to effectively improve the performance of OLEDs,in this work,magnetic alloy nanoparticles,magnetic nanocomposites and silver nanoparticles were allowed to dope in hole-transport layer of OLEDs.The main research contents of this paper are as follows:1.The surface carbon-coated NPs?FePt@C and Co Pt@C?were prepared via controlled pyrolysis of the heterobimetallic polymers.We have tried to dope FePt@C and CoPt@C into OLED device as a composite HIL to improve the performance of the evices by ptimizing the doping oncentration of nanoparticles.Compared with the control device with a tandard architecture,the urrent efficiencies of fluorescent green OLED can be enhanced by 47.1%and 48.5%by mixing the surface carbon-coated magnetic FePt?0.5 wt‰?and CoPt?0.5wt‰?alloy NPs into poly?3,4-ethylenedioxythiophene?:poly?styrenesulfonate??PEDOT:PSS?,yielding the maximum values of 5.40 cd A^-1 and 5.45 cd A^-1,respectively.This is mainly attributable to the collective effects of light-scattering,localized surface plasmon resonance and increased electron trap density induced by magnetic alloy NPs.2.A series of magnetic composite nanoparticles Fe₃O₄@G,Fe₃O₄@SiO₂,Fe₃O₄@Au were designed and synthesized.Then,Fe₃O₄@G,Fe₃O₄@SiO₂ and Fe₃O₄@Au NPs were allowed to dope into OLED device forming composite HILs,realizing 35%improvement of efficiency by taking advantage of the collective effects of light-scattering,localized surface plasmon resonance?LSPR?and magnetic effect,induced by the magnetic NPs in the HIL.The mechanism of efficiency improvement,was explored by X ray photoelectron spectroscopy?XPS?,PL spectra,transmission spectra as well as theoretical calculation with the finite element method?FEM?.3.It is generally known that the distance between metal nanoparticles and the excitons can significantly influence the degree of surface plasmon coupling.We reported our effort to develop efficient blue phosphorescent organic light-emitting diodes?PhOLEDs?by embedding an ultrathin layer of Ag nanoparticles?NPs?in different positions in OLEDs and studied their influences on the efficiency.We optimized the device performance by controlling the distance between silver nanoparticles and the emitting layer.It was finally found that when the distance between silver nanoparticles and the emitting layer is 20nm,the energy transfer between exciton and LSP induced metal is optimal.Compared with the control device with a conventional organic HTL,the current efficiency of the PhOLEDs with a Ag-NPs-embedded HTL were enhanced by2.5 times.In addition,the efficiency roll off has also been alleviated.Furthermore,we undertook a deep explore ation on the mechanism of Ag nanoparticle in OLED by the finite element method?FEM?,which gave analysis on the interaction of metal nanoparticles and excitons and near field distribution of Ag nanoparticle.