TPBI, electron transport

Fig. 8.11 Efficiency versus luminance of devices containing dendrimer 4 (lr(ppy)3). The electron-transporting BCP, respectively, TPBI layers were evaporated onto the spin-coated dendri-mer CBP/TCTA blend. Reproduced from [76] with permission ofWiley-VCH Verlag GmbH.

Gao et al. [273] reported the fabrication of a bright-blue electroluminescent device based on an emissive dopant, a substituted ter-PV,l,4-bis[4-(2-trimethylsilylvinyl)styryl]-2,5-dibutoxybenzene (BTSB) and an electron transporter, AT-arylbenzimidazole (TPBI). The device doped with 10-wt% BTSB had a threshold voltage of about 3.8 V and a current efficiency of 3.2 cd A at a current density of 20 mAcm . The device achieved a brightness of 11,000 cd m 2 at a current density of 360 mA cm 2, which is com-... 

Figure 7.4 shows the structures of typical electron transport organic semiconductors. Alq3, which can act both as an electron conductor and green emitter, was used by Tang in his first OLEDs and is still in use today. Besides metal complexes electron deficient heterocycles are frequently used as electron transport materials. The triazine derivative TPT [14, 15], the oxadiazole PBD and its spiro analogue spiro-PBD [16, 17] and the benzimidazole TPBI serve as typical examples. 2,9-Dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) has a very low HOMO level and is often used as a hole blocking layer. 

Fig. 8.10 Structures of electron- and hole-transporting materials commonly used in combination with dendrimers. TCTA 4,4, 4"-tris(N-carbazolyl)triphenylamine CBP 4,4 -bis-(N-car-bazolyl)biphenyl TPBI 1,3,5-tris(2-N-phenylbenzimidazolyl)benzene BCP Bathocuproine PBD 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-l, 3,4-oxadiazole.

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