Synthesis And Photoelectric Properties Of Blue-light-emitting Polymers Containing Sulphone Moiety And P-type Polymers With Shallow HOMO

Organic/Polymer Light-Emitting Diodes(O/PLEDs)have the characteristics of autoluminescence,ultra-thinness,ultra-light weight,high contrast,wide viewing angle,fast response and low-power consumption.Compared with small molecular,polymer luminescent materials have better performance in film-forming with which large area PLED can be prepared by solution processing methods such as spin coating and ink jet printing.It will contribute to the further reduction of manufacturing cost and the realization of commercial production.Among the three primary colors,the development of high-efficient blue-emitting polymers is the most challenging one,because it is difficult to meet a wide bandgap and excellent charge injection and transportation for the emitter simultaneously.Sulfone is a strong electron-withdrawing group with the sulfur atom at the highest valence state,endowing it with good chemical stability and high electronic affinity.The introduction of moieties containing sulfone into the backbone of emitting polymers can effectively enhance electron injection and transport to further improve electroluminescence performance.Compared with traditional devices which are fabricated with single emitting layer,tandem organic electroluminescent devices which are based on multiple independent electroluminescent units can achieve higher current efficiency and longer lifetime.P-type polymers with shallow HOMO level can be used as charge generation materials to develop highly efficient tandem PLED by solution-based processes.1)Polymer PFCz SO and PFSO-Ts were synthesized by introducing carbazole on t he sidechain and triarylamine into the backbone of poly[(fluorene)-co-dibenzothiophene-S,S-dioxide]s,respectively.The ICT effect between dibenzothiophene-S,S-dioxide and carbazole/ triarylamine was restricted by rational molecular design and pure blue emitting was maintained.The hole transport segment can effectively elevate polymers' HOMO level and reduce hole-injection barrier,which can facilitate hole injection and thus lead to more balanced charge carrier transport in the emissive layer.With single-layer light-emitting devices,both PFCzSO and PFSO-Ts show much better electroluminescence performance than poly[(fluorene)-co-dibenzothiophene-S,S-dioxide]s.A maximum luminous efficiency of 5.52 c d A-1 with a CIE coordinates of(0.17,0.17)was obtained from PCz25 SO.2)Novel blue light-emitting PPF-FSOs and PPF-SOFs were synthesized via introducing spiro[fluorene-9,9'-thioxanthene-S,S-dioxide] isomers(2,7-diyl and 2',7'-diyl)(FSO/SOF)into the polyfluorenes backbone,respectively.With the increasing contents of FSO and SOF moieties,the absorption and PL spectra of PPF-FSOs show slight red shift,while that of PPF-SOFs exhibit blue shift.The distinctly narrowing emission was observed with the increasing content of isomers in the polymers.The nonconjugated SOF moiety in the polyfluorene backbone can effectively disturb the conjugation length and realize a deep blue emission with CIE coordinate around(0.16,0.08).Owing to the enhanced electron injection from spiro[fluorene-9,9'-thioxanthene-S,S-dioxide],the single layer devices based on t hese polymers exhibited much better electroluminescence performance in comparison with polyfluorene no m atter the sulfone is in the banckbone or sidechain of those polymers.A EQEmax of 3.76% was obtained from PPF-SOF15 based device,which denotes a threefold increase compared to PPF based device.3)Nonconjugated 9,9-dimethyl-thioxanthene-10,10-dioxide(2,7-diyl and 3,6-diyl)were synthesized and introduced into polyfluorenes and poly(2,7-carbazole).The 9,9-dimethyl-thioxanthene-10,10-dioxide effectively disturb the conjugation of polymers,resulting in the blue-shift and narrowing of spectra.The sulfone can validly improve electron injection and transport.As a result,highly efficient polyfluorene derivatives with CIEy ? 0.1 were obtained.PF-27SO20 exhibits a maximum luminous efficiency of 2.30 cd A-1 and a EQEmax of 4.05%,with CIE coordinates of(0.15,0.08).PCz-27 SOs and PCz-36 SOs are the first reported deep blue poly(2,7-carbazole)s constructing a D-A structure.4)A series of p-type polymers containing triphenylamine and phenothiazine were synthesized.Oligo(ethylene glycol)(OEG)was grafted on the sidechain of these polymers,making them solube in solvent with medium polarity,such as dioxane,dioxolane,and insoluble in strong polar solvent,such as 2-methoxyethanol,methanol.All of the p-type polymers are featured with shallow HOMO level and high hole mobilities.Furthermore,all-organic interconnecting layer p-type polymers/FPyBr were tested to have efficient charge generation,which indicates that all-organic charge generation layer based tandem PLEDs can be expected.