Thermally activated delayed fluorescence (TADF) properties of a dicarbazole-triazine compound, 9-(4,6-diphenyl-1,3,5-triazin-2-yl)-9'-phenyl-3,3'-bicarbazole (CzT), and its OLED characteristics were investigated. An estimated small energy gap of about 90 meV between the singlet and triplet energy states of CzT made the up-conversion of triplet excitons back to a singlet state possible. The origin of the observed delayed fluorescence has been shown to be thermally activated delayed fluorescence. An organic light emitting diode (OLED) with CzT as an emitter showed the maximum external quantum efficiency (EQE) of 6%. For comparison, another carbazole-triazine derivative of 3-(2'-(4,6-diphenyl-1,3,5-triazin-2-yl)-[1,1'-biphenyl]-2-yl)-9-phenyl-9H-carbazole (PhCzTAZ) with a similar structure was also studied. PhCzTAZ showed a low fluorescence quantum yield with no TADF.

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We have synthesized and characterized a novel thermally polymerizable triaryldiamine monomer (VB-FNPD) possessing a styrene-functionalized 9,9-diarylfluorene core and have used time-of-flight transient photocurrent techniques to investigate the hole transport properties of its solution-processed and subsequently thermally cured (170 C) polymer films. This novel polymeric material exhibits nondispersive hole transport behavior with a high hole drift mobility (up to 10 À4 cm 2 V À1 s À1 ). The film displayed remarkable ambient stability, even when exposed to air for one month. We tested the thermally generated polymer film as a hole transport material in organic light-emitting diodes incorporating tris(8-hydroxyquinolate) aluminium (Alq 3 ) as the emission and electron transport layer. The device exhibited a maximum external quantum efficiency (h ex ) of 1.4%, significantly better than that of the device prepared using the corresponding model compound VB-model (h ex ¼ 1.1%).

Abstract— A new approach to full‐color printable phosphorescent organic light‐emitting devices (P2OLEDs) is reported. Unlike conventional solution‐processed OLEDs that contain conjugated polymers in the emissive layer, the P2OLED's emissive layer consists of small‐molecule materials. A red P2OLED that exhibits a luminous efficiency of 11.6 cd/A and a projected lifetime of 100,000 hours from an initial luminance of 500 cd/m2, a green P2OLED with a luminous efficiency of 34 cd/A and a projected lifetime of 63,000 hours from an initial luminance of 1000 cd/m2, a light‐blue P2OLED with a luminous efficiency of 19 cd/A and a projected lifetime 6000 hours from an initial luminance of 500 cd/m2, and a blue P2OLED with a luminous efficiency of 6.2 cd/A and a projected lifetime of 1000 hours from an initial luminance of 500 cd/m2 is presented.