The conjugation effects on the luminescence properties of oligophenylenes for the OLED

We synthesized novel phenyl-complexes as blue-emitting materials. The absorption maximum of 1,4′:1′,1ʺ:2ʺ,1‴,4⁗,1⁗—quinquephenyl (BBPB) and 2ʺ,5ʺ-bis(1,1′-biphenyl-4-yl)—1,4′:1′,1ʺ:4ʺ,1‴:4‴,1⁗-quinquephenyl (TTBPB) were located at 290 and 276 nm. The peak PL emission of TTBPB appears at 410 nm and that of BBPB appears at 374 nm with a shoulder at 398 nm, which indicate that the two types of aggregations are formed at the solid state. The dramatic difference in fluorescence quantum yield of the oligophenylenes is due to the steric twist of the two biphenyl groups of BBPB. The four biphenyl groups of TTBPB are conjugated to a generated pentaphenylene moiety. As expected, the oligophenylene derivatives exhibit low current density and the electroluminescence intensity is not high, due to less extended conjugation effects of phenylene groups. The relatively high intensity of TTBPB on organic light-emitting diode (OLED) can be explained by the conjugation effects of biphenyl groups of oligophenylenes.