Solution‐Processible 2,2′‐Dimethyl‐biphenyl Cored Carbazole Dendrimers as Universal Hosts for Efficient Blue, Green, and Red Phosphorescent OLEDs

Abstract

A series of solution‐processible 2,2′‐dimethyl‐biphenyl cored dendrimers, namely G1MP, G2MP, and G3MP, is designed and synthesized by tuning the generation of periphery carbazole dendron. The resulting dendrimers all show excellent solubility in common organic solvents, and their high‐quality thin films can be formed via spin‐coating with a root‐mean‐square roughness in the range of 0.38–0.54 nm. G3MP, which contains the third‐generation carbazole dendron, has the greatest potential among those made here as an ideal universal host for multicolored triplet emitters. G3MP exhibits good thermal stability, with a glass transition temperature of 368 °C, a triplet energy as high as 2.85 eV enough to prevent the loss of triplet excitons, and suitable HOMO/LUMO levels of –5.30/–2.11 eV to facilitate both hole and electron injection and transport. When using G3MP as the host, highly efficient deep‐blue, blue, green, and red phosphorescent organic light‐emitting diodes (PhOLEDs) are successfully demonstrated, revealing a maximum luminous efficiency up to 18.2, 28.2, 54.0, and 12.7 cd A–1 with the corresponding Commission Internationale de L'Eclairage (CIE) coordinates of (0.15, 0.23), (0.15, 0.35), (0.38, 0.59), and (0.64, 0.34), respectively. The state‐of‐art performance indicates that dendritic hosts have a favorable prospect of applications in solution‐processed white PhOLEDs and full‐color displays.

Solution-processed blue phosphorescent OLEDs with carbazole-based polymeric host materials

“…In the same spirit, a styrene-derived poly(carbazole) (PVAK) varying from PVK by the polymeric unit gave blue PLEDs with a CE of 18.25 cd/A while using FIrpic as the dopant [52]. Investigations on carbazole-based hosts were not limited to non-conjugated polymers and polymeric hosts with a disrupted p-conjugated main chain [53][54][55] or dendrimers [56,57] also furnished high performances with FIrpic or even more blue triplet emitters.…”

High efficiency blue fluorescent organic light-emitting diodes using a conventional blue fluorescent emitter

“…8,9 The theoretical maximum QE has already been realized in the phosphorescent OLEDs. [15][16][17][18][19][20] As a replacement of the blue phosphorescent OLEDs, blue thermally activated delayed fluorescent (TADF) devices have been explored and a high QE of 19.5% was achieved using bis [4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone (DMAC-DPS) as a TADF emitter. [15][16][17][18][19][20] As a replacement of the blue phosphorescent OLEDs, blue thermally activated delayed fluorescent (TADF) devices have been explored and a high QE of 19.5% was achieved using bis [4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone (DMAC-DPS) as a TADF emitter.…”

Solution-Processed Blue/Deep Blue and White Phosphorescent Organic Light-Emitting Diodes (PhOLEDs) Hosted by a Polysiloxane Derivative with Pendant mCP (1,3-bis(9-carbazolyl)benzene)

“…31 Carbazole derivatives are established as hosts for PhOLEDs due to carbazole's high triplet energy and favorable hole-transporting properties. [32][33][34][35] The small-molecule mCP [1,3-bis(9-carbazolyl)benzene] which has a triplet energy of 2.9 eV is widely used in this context. [36][37][38][39][40][41] However, mCP tends to crystallize as a consequence of its rather low T g (glass transition temperature, 60 °C).…”