Polymers Derived from 3,6-Fluorene and Tetraphenylsilane Derivatives: Solution-Processable Host Materials for Green Phosphorescent OLEDs

Abstract

We have synthesized two fluorene-based polymeric host materials, P1 and P2, through palladiumcatalyzed Suzuki couplings of monomers containing tetraphenylsilane and 3,6-disubstituted fluorene frameworks, respectively. The resultant copolymers exhibited high glass transition temperatures (T g g 215°C) and excellent thermal stability. The conjugation lengths of polymers P1 and P2 were effectively confined through the presence of the 3,6-linkages and silane units in the polymer skeleton. The structural features endowed these copolymers with UV-violet emissions in the solid state, together with high triplet energies (E T ) 2.60 eV), which were sufficiently high for P1 and P2 to serve as appropriate hosts for green-emitting phosphors. In the case of polymer P2, the incorporation of pendent carbazole groups increased the HOMO level markedly and balanced the rates of charge injection and transportation. Employing P2 doped with green-emitting fac-tris(2-phenylpyridine)iridium as the emissive layer, we fabricated highly efficient polymer light-emitting diodes (32 cd/A, 9.2%) that exhibited significantly enhanced EL performance relative to that of the system employing P1 (14.5 cd/A, 4.2%).

Carbazole-based polymers as hosts for solution-processed organic light-emitting diodes: Simplicity, efficacy

“…Consequently, P54 showed the high triplet energy of 2.96 eV, rendering this polymer capable to host FIrpic and surpassing most of the polymeric hosts ever reported [54,55,124,135,151,152]. In the common device structure ITO/PEDOT:PSS (40 nm)/P54:FIrpic (40 nm)/TPCz (50 nm)/LiF (1 nm)/Al, a maximum CE of 23.3 cd/A was obtained at the practical brightness of 116 cd/m 2 (see Table 1).…”

“…Tremendous efforts are thus devoted to prepare wide bandgap polymeric hosts. However, availability of suitable polymeric hosts for blue phosphorescent dopants is still lagging far behind that of the other colors [53][54][55]. Recently, several examples of wide bandgap polymeric hosts based on a p-conjugated interrupted polymer backbone were developed [56][57][58][59].…”

Solution-processed blue phosphorescent OLEDs with carbazole-based polymeric host materials

“…Among the most important features, the charge transportation, the film-forming ability, the thermal stability, the HOMO-LUMO gap and the energy level of the triplet excited state can be cited as the main criteria to consider for designing an efficient host material [31]. Regarding PLEDs, development of blue-emitting devices is still far behind the other colors due to the lack of suitable polymeric hosts [32][33][34]. Up to now, poly(N-vinylcarbazole) (PVK) has undoubtedly been one of the most common polymeric host for http wide bandgap emitters [35][36][37].…”

Distyrylbenzene-based segmented conjugated polymers: Synthesis, thin film morphology and chemosensing of hydrophobic and hydrophilic nitroaromatics in aqueous media

“…In this context, an efficacious concept of macromolecular design aiming to customize the physical and electronic properties of conjugated polymers consists in the regular insertion in the polymer backbone of atomic or molecular motifs which tailor the π-conjugation length. Thus, a variety of regularly segmented conjugated polymers (SCPs) have been synthesized by linking aromatic segments of discrete size with spacers such as biphenylene [8], binaphthylene [9], paracyclophane [10], linear alkylene [11,12] and oxyethylene chains [13], oxygen atoms [14], silicon atoms [15,16] and sp 3 -carbon atoms of the norbornylene [17], fluorenylidene [18] and isopropylidene groups [19][20][21] all of which break conjugation in a controlled manner.…”