Effect Of Dopant On The Configuration, Property Of PEDOT Conducting Polymer And Its Application Performance As Anode Buffer Material

The configuration and property of poly?3,4-ethylenedioxythiophene??PEDOT?conducting polymer depend on the structure and property of its dopant.Poly?styrene sulfonic acid??PSS?,a kind of macromolecular dopant,has been applied to prepare solution-processable PEDOT:PSS conducting polymer,which is well-known as the most remarkable conducting polymer.PEDOT:PSS has applied as a standard anode buffer material?ABM?in organic electronic devices including phosphorescent organic light emitting diode?PHOLED?and organic-inorganic hybrid perovskite solar cell?PSC?.However,there still exist drawbacks for PEDOT:PSS,such as relatively low work function?WF?,poor homogeneity,inferior waterproofness and weak conductivity,limiting the development of the semiconductor and device configuration of organic electronic devices.Therefore,there is of significance to develop new dopant for overcoming the above deficiencies of PEDOT:PSS as well as reveal the influence on the configuration and property of its PEDOT conducting polymer and further enhancing the performance in ABM.In this dissertation,we applied methylnaphthalene sulfonate formaldehyde condensate?MNSF?,lignosulfonate?LS?and perfluorooctanoic acid?F?as dopant to prepare novel solution-processable PEDOT conducting polymer to overcome the above deficiencies of PEDOT:PSS.The relationship between the characteristics of various dopant and PEDOT:dopant complex was investigated.The hole injection/extraction capability of the new PEDOT:dopant complexes as ABM in PHOLED and PSC devices were also investigated.Firstly,MNSF was applied as dopant to prepared novel solution-processable PEDOT:MNSF conducting polymers,and the defects of low WF and poor homogeneity mentioned above were resolved.It was found that PEDOT:MNSF-1:6 possesses excellent homogeneity,which was revealed by the combination of element analysis and X-ray photoelectron spectroscopy?XPS?measurements.Phase separation experiment and conductive atomic force microscopy?c-AFM?were used to further investigate the homogeneity of PEDOT:MNSF-1:6 film.The MNSF dopant with small molecular weight and branched structure was proposed to effectively reduce the content of free dopant in PEDOT:MNSF-1:6system as well as reduce the scale of phase separation,resulting in an improved film homogeneity.Based on the superior properties mentioned above,PEDOT:MNSF-1:6 were applied as ABM in PHOLED and PSC,and a maximum current efficiency(CE_max)of 33.4 cd·A^-1 and a conversion efficiency?PCE?of 13.1%were obtained,respectively,outperforming the PEDOT:PSS-based devices exhibiting a CE_max of 25.1 cd·A^-1 and a PCE of 11.5%owing to the enhanced WF and homogeneity of ABM.Our research displays a promising future of MNSF as a cheap and widely available alternative of PSS.Moreover,a clear map is provided for the design of dopant for PEDOT considering the structure of dopant.Secondly,LS was applied as dopant to prepare novel solution-processable PEDOT:LS conducting polymer,and the defects of low WF,poor homogeneity and inferior waterproofness mentioned above were resolved.The covalent bonding between LS and PEDOT,which was confirmed by the combination of absorption spectroscopy,infrared spectroscopy,gel permeation chromatography?GPC?,AFM and phase separation experiment,is speculated to be the reason for the improvement of the film homogeneity.The thermal crosslinking activity of LS can result in a dense PEDOT:LS film with excellent waterproofness which was confirmed by GPC and contact angle measurement.Inspired by the aforementioned merits,PEDOT:LS was applied as ABM in PSC.The PEDOT:LS-based PSC shows an enhanced PCE of 12.85%,outperforming the PEDOT:PSS-based device exhibiting a PCE of 12.10%owing to the enhanced WF and homogeneity of ABM.More importantly,the PEDOT:LS-based PSC shows a higher long-term stability compared with PEDOT:PSS-based device due to the excellent waterproofness of ABM.Our research provides a novel perspective for the design of dopant for conducting polymer based on lignin and promote the functional and high-valued applications of lignin.Finally,in order to further enhance the application potential of LS-based PEDOT conducting polymer,an additional dopant of F with small molecular weight was applied,and the conductivity of LS-based PEDOT conducting polymer was improved greatly from 0.0208S·cm^-1 to 0.1250 S·cm^-1.The synergistic mechanism of the double dopant system in the polymerization process was systematically studied by absorption spectroscopy,dynamic light scattering,AFM,electron paramagnetic resonance spectroscopy and X-ray diffraction measurements.It was found that the polymerization,doping and stacking of PEDOT,the key influential factors on conductivity of PEDOT complex,can be improved by the addition of F with a lot of fluorine atoms which possess strong hydrophobicity and electron-withdraw capabilities.In addition,the excellent optical,electrochemical and waterproof properties of the LS-based PEDOT conducting polymer were retained.Our research provides a promising strategy to design high-conductive PEDOT complex by using double dopant system.