Solution-processable, single-layer, blue organic light-emitting diodes employing dual emitting cores of hybridized local and charge-transfer units

Two novel dual emitting core hybridized local and charge-transfer emitters of 4',4 '''-(1,1'-((9-(heptadecan-9-yl)-9H-carbazole-2,7-diyl)bis(4,1-phenylene))bis(1H-p-henanthro [9,10-d]imidazole-2,1-diyl)) bis(N,N-diphenyl-[1,1'-biphenyl]-4-amine) and 4',4 '''-(1,1'-((9-(heptadecan-9-yl)-9H-carbazole-2,7-diyl)bis(3,1-phenylene))bis(1H-phenanthro[9,10-d]imidazole-2,1-diyl))bis(N,N-diphenyl-[1,1'-biphenyl]-4-amine) were designed and synthesized by introducing two hybridized local and charge-transfer units for single-layer, solution-processable, and blue organic light-emitting diodes (OLEDs). Their absorption, photoluminescence, hybridized local arid charge-transfer characteristics, thermal stability and electrochemistry were systematically studied. The single-layered devices by using them as emitters showed efficient blue emission with a maximum brightness 5521 cd/m(2) for 4',4 '''-(1,1'-((9-(heptadecan-9-yl)-9H-carbazole-2,7-diyl)bis(4,1-phenylene))bis(1H-p-henanthro[9,10-d]imidazole-2,1-diyl))bis(N,N-diphenyl-[1,1'-biphenyl]-4-amine) and 4403 cd/m(2) for 4',4 '''-(1,1'((9-(heptadecan-9-yl)-9H-carbazole-2,7-diyl)bis(3,1-phenylene))bis(1H-phenanthro [9,10-d]imidazole-2,1-diyl))bis(N,N-diphenyl-[1,1'-biphenyl]-4-amine). The maximal efficiencies of the former were up to 3.71 cd/A, 233 lm/W, and 2.88%. Furthermore, at the high luminescence, the device still indicated good performance with relative low efficiency roll-off. The relationships of structures and properties were also discussed. Most importantly, we provided a new method to construct solution processable small molecules for highly efficient single-layer OLEDs. (C) 2016 Elsevier Ltd. All rights reserved.