Synthesis And Electroluminesecent Properties Of Blue Light And Hole Transport Materials Based On Plolymer

Organic/Polymer Light Emitting Diodes（O/PLEDs）have the advantages of active luminescence,low cost,light weight,wide viewing angle and low energy consumption.Besides,PLEDs can be prepared by solution process in large areas,therefore commercial development can be achieved.In this paper,a series of solution-processable blue light emitting polymers and hole transport polymer s were designed and synthesized to reseach their electroluminescent properties.A new compound of 2,8-dibromo-14,14-dioctyl-14H-benzo[b]benzo[5,6] anthracene[1,2-d]thiophene-9,9-dioxide（NFSO）was synthesized and introduced into the polyfluorene（PFO）derivatives to obtain a series of copolymer PNFSOs.The NFSO unit contains electron-withdrawing sulfone group which can improve electron injection and transport properties of the polymer.At the same time,the distorted structure of NFSO can reduce the red shift caused by the intramolecular charge transfer effect（ICT）.Therefore,the NFSO unit is able to maintain the blue emission spectrum and increase the charge carriers transport balance of the polymerized derivatives simultaneously.Electroluminescent devices adopting the polymer PNFSOs as emmiting layer were constructed with a structure of ITO/PEDOT/PVK（15nm）/EML（60nm）/Ba/Al.The PNFSO05-based device exhibits excellent luminescence properties with a maximum luminous efficiency of 2.60 cd A^-1 and CIE coordinates of（0.17,0.11）.PCz-37 SOs and PCz-28 SOs were synthesized by introducing 3,7-dibromo-2,8-dioctyl-S,S-dioxide-dibenzothiophene（37SO）and 2,8-dibromo-S,S-dioxide –dibenzothiophene（37SO）into the polycarbazole backbone,respectively.37 SO has a long alkyl chain in 2,8 position leding to a big twist angle between the carbazole unit and the 37 SO unit,so that the intramolecular charge transfer（ICT）effect can be suppressed.On the other hand,28 SO has a weaker conjugation with carbazole unit.Furthermore,the structure of PCz-28 SOs is more distorted,which can inhibit moleculat aggregation.Therefore both of the two polymers showed a pure blue emission spectrum.Based on single-layer device structure ITO/PEDOT:PSS/Polymer/Cs F/Al,PCz-37SO20 and PCz-28SO20 showed excellent luminescence properties with the maximum current efficiency of 1.61 cd A^-1 and 2.69 cd A^-1and the CIE coordinates of（0.16,0.11）and（0.16,0.13）,respectively.A thermally crosslinkable hole-transporting poly（indenofluoreneco-triphenylamine）copolymer（X-IFTPA）containing a vinyl-functionalized triphenylamine moiety was synthesized and described.This copolymer exhibited an exothermal peak at 125°C in the first heating/cooling cycle of a differential scanning calorimetry study,indicating that crosslinking occurred.Flat and uniform films were formed by spin casting X-IFTPA from chlorobenzene solution.Crosslinking can be finished by thermally annealing the film at 150 °C for 24 min,which can be confirmed by reflectance Fourier transform infrared spectroscopy and UV-Vis absorption spectra.Multi-layer polymer light-emitting diodes（PLEDs）incorporating X-IFTPA as the hole transport layer and a green-light-emitting copolymer as the emissive layer exhibited enhanced luminous efficiency relative to that of a control device without a hole transport layer,the maximum current efficiency was increased from 6.19 cd A^-1 to 11.57 cd A^-1.Thus,the developed cross-linkable copolymer X-IFTPA is a promising material for the construction of efficient PLEDs.