Charge-transporting blue emitters having donor and acceptor moieties

• Hole-transporting and electron-transporting emitters were synthesized.
• Hole mobility exceeded 10−3 cm2 V−1 s−1.
• Electron mobility exceeded 10−3 cm2 V−1 s−1.
• The molecular mixtures with the phosphorescent dye showed white emission.

Hole-transporting derivative of phenanthro[9,10-d]imidazole and triphenylamine and electron-transporting derivative of carbazole and 1,8-naphthalimide were synthesized and characterized. The synthesized compounds exhibited high thermal stability with the temperatures of the onsets of the thermal decomposition (463 °C and 438 °C). They showed blue emission in solutions. Relatively high hole mobility of 10−3 cm2 V−1 s−1 for the layer of 2-[4-(diphenylamino)phenyl]-1-phenyl-1H-phenanthro[9,10-d]imidazole, and electron mobility exceeding 10−3 cm2 V−1 s−1 for the layer of 2,7-di((N-(2-ethylhexyl)-1,8-naphthalimide)-4-yl)-9-(2-ethylhexyl)-9H-carbazole were recorded by time of flight technique. The molecular mixtures consisting of the newly synthesized dyes with the commercial phosphorescent dye bis(2-phenylbenzothiozolato-N,C(2′))iridium(acetylacetonate) [bt2Ir(acac)] and poly[9-(2,3-epoxypropyl)carbazole] as a polymer host were prepared and studied. The colour characteristics of the photoluminescence of the obtained molecular mixtures were found to be close to those of the white light. It is suggested that in the studied molecular mixtures both Ir-based phosphorescent and fluorescent dyes can effectively absorb excitons from the polymer matrix.

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