Dibenzothiophene dioxide-benzofuro carbazole based bipolar host material for yellow and red phosphorescent OLEDs

Electronic properties of carbazole/biphenylamino functionalized sulfone‐based host materials

“…For the aim to get more detailed information about the effect of the introduced carbazole and biphenylamino groups on the electronic properties of SO 2 -based host materials, we use quantum-chemical techniques to characterize the ground (S 0 ) and lowest triplet excited (T 1 ) states of a series of sulfonyl host materials. Dibenzo[b,d] thiophene 5,5-dioxide (DBTO, in Figure 1) and their carbazole or biphenylamino functionalized derivatives [42,43] will be used for our discussion in this work.…”

A universal bipolar host based on isonicotinonitrile and carbazole for efficient red, green and blue PhOLEDs

“…Luckily, the host-guest system was found to be effective to alleviate the concentration caused quenching issue by dispersing the heavy metal emitters homogeneously in a proper host. [6][7][8][9][10][11][12] Thus, the host materials are of equal importance compared to the emitters to achieve high electroluminescent (EL) performance.…”

“…(2) good thermal stability to withstand the high temperature during fabrication and the Joule heat generated in the operating process as well as maintain the morphological stability; (3) appropriate highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels with the adjacent layers to facilitate the carrier transportation so as to lower the driving voltage. 6,8,[11][12][13][14][15] Besides, it has been well established that keeping charge balance is of vital importance to elevate the performance of PhOLEDs, and bipolar hosts comprising an electron rich donor (D) and electron deficient acceptor (A) have been proved to be able to fulfill this demand. 9,[16][17][18][19][20] By simultaneously reducing the charge injection barriers of both holes and electrons, bipolar hosts could balance the carrier transport and expand the charge recombination zone to effectively improve the EL performance.…”

“…Carbazole is a widely used building block for hole transport due to its good electron donating ability, high E T , easy modification on its backbone and high thermal stability. 10,11,15,18,26,27 Isonicotinonitrile, also known as 4-cyano substituted pyridine, which could benefit from the good electron transport ability and high thermal stability of both of the two groups, is a potential acceptor for constructing bipolar hosts and D-A type emitters. [28][29][30] Li et al introduced a 3-cyanopyridine unit to the widely used host 1,3-di(9H-carbazol-9-yl)benzene (mCP) to construct a bipolar host 3-PyCNmCP and an EQE max of 24.7% was obtained when hosting green PhOLEDs.…”

Phosphine Sulfide-Based Bipolar Host Materials for Blue Phosphorescent Organic Light-Emitting Diodes

“…Bipolar hosts, generally prepared by combining the donor (D) and acceptor (A) units into a molecular skeleton (i.e., D–A molecules), are capable of achieving a broad recombination zone and balanced charge in the emitting layer (EML), so they are considered one of the most promising types of hosts to realize highly efficient PhOLEDs [ 6 , 7 , 8 ]. Up until the present, the bipolar hosts for green, yellow, and red phosphorescent emitters have made commendable progress [ 9 , 10 , 11 , 12 ], while it is still challenging to develop superior blue hosts because the blue phosphors inherently possess high triplet energy ( E T ) levels [ 13 , 14 , 15 ], thus the E T of the hosts should be accordingly elevated to prevent the reverse energy transfer from the guests back to the hosts and to effectively confine triplet excitons on the guests. However, the non-negligible intramolecular interactions in D–A molecules would produce a low energy charge transfer (CT) state, which brings down the E T levels [ 16 ].…”