Synthesis and Characteristics of Organic Red‐Emissive Materials Based on Phenanthro[9,10‐d]imidazole

Abstract

Red emission is one of the three primary colors that are essential for the realization of full‐color displays and solid‐state lightings. A high solid‐state efficiency is a crucial factor for the applications in organic light‐emitting diodes (OLEDs). In this work, two new donor‐acceptor‐donor type phenanthro[9,10‐d]imidazole (PIM)‐based derivatives, (2Z,2′Z)‐2,2′‐(1,4‐phenylene)bis(3‐(4‐(1‐phenyl‐1H‐phenanthro[9,10‐d]imidazol‐2‐yl)phenyl)acrylonitrile) (PIDSB) and 2,3‐bis(4′‐(1‐phenyl‐1H‐phenanthro[9,10‐d]imidazol‐2‐yl)‐[1,1′‐biphenyl]‐4‐yl)fumaronitrile (PIDPh), are designed and synthesized. Both of them possess high thermal stabilities. PIDPh shows typical characteristics of aggregation‐induced emission enhancement, while PIDSB displays an aggregation‐caused quenching effect. They both exhibit significant red‐shifted emissions compared with PIM owing to intramolecular charge transfer. In the film state, the emission peaks of PIDSB and PIDPh are located at 538 nm and 605 nm with high photoluminescent quantum yields of 63.82 % and 41.26 %, respectively. The non‐doped OLED using PIDPh as the active layer shows the maximum external quantum efficiency of 2.06 % with a very low efficiency roll‐off, and exhibits the electroluminescent peak at 640 nm with a Commission Internationale de l′Éclairage coordinate of (0.617,0.396), meeting well the criteria of red OLEDs.

Efficient Red Electroluminescence From Phenanthro[9,10‐d]imidazole‐Naphtho[2,3‐c][1,2,5]thiadiazole Donor‐Acceptor Derivatives

“…Similarly, PINzPCN also showed better performance in doped device and the maximum EQE was improved to 5.92%. To the best of our knowledge, the device performance of PINzP and PINzPCN is fairly good among red‐emitting fluorescent materials [13–38] …”

“…A more general approach to deliver red emission is based on the donor-acceptor (DÀ A) skeleton. [13][14][15][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] The most classic redemitting DÀ A molecule is DCJTB. [19,20] Other red-emitting DÀ A materials are constructed based on various donors and acceptors and some of them have exhibited high efficiency.…”

“…[19,20] Other red-emitting DÀ A materials are constructed based on various donors and acceptors and some of them have exhibited high efficiency. [14,15,[21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] The most commonly adopted donors are arylamine derivatives such as carbazole, [23,27,33] triphenylamine, [15,[24][25][26][27][28][29][30] phenothiazine, [37] phenoxazine, [38] etc. In this work, we use phenanthro [9,10-d] imidazole as the donor because of its high photoluminescence quantum yield (PLQY) and rigid molecular structure.…”

“…However, these planar poly‐hydrocarbons are prone to concentration quenching due to strong π–π interactions. A more general approach to deliver red emission is based on the donor‐acceptor (D−A) skeleton [13–15,19–38] . The most classic red‐emitting D−A molecule is DCJTB [19,20] .…”

“…The most classic red‐emitting D−A molecule is DCJTB [19,20] . Other red‐emitting D−A materials are constructed based on various donors and acceptors and some of them have exhibited high efficiency [14,15,21–38] . The most commonly adopted donors are arylamine derivatives such as carbazole, [23,27,33] triphenylamine, [15,24–30] phenothiazine, [37] phenoxazine, [38] etc.…”