Wen-Li Jia

Diarylamino functionalized pyrene derivatives for use in blue OLEDs and complex formation

Three new 2,2′-dipyridylamino functionalized pyrene derivatives, 1-pyrenyl-2,2′-dipyridylamine (1), 4-(1-pyrenyl)phenyl-2,2′-dipyridylamine (2), and 4-[4′-(1-pyrenyl)biphenyl]-2,2′-dipyridylamine (3) have been synthesized and fully characterized. For comparison of electronic properties, a diphenylamino functionalized molecule 4-[4′-(1-pyrenyl)biphenyl]diphenylamine (4) has also been synthesized. Compounds 1–4 are bright blue emitters in solution and in the solid state with λmax at ∼420–460 nm and a high emission efficiency in solution. All four compounds form amorphous glasses with Tg values of 66 °C, 79 °C, 165 °C, and 98 °C, respectively. The electronic properties of the four compounds were examined by spectroscopic methods, cyclic voltammetry and Gaussian 98 molecular orbital calculations. The utilities of this class of molecules in OLEDs have been demonstrated by EL devices of compounds 3 and 4, which showed that 3 can function as a bright blue emitter and an electron transport material in a double-layer device while 4 can function as a bright blue emitter and a hole transport molecule in a triple-layer device. The dipyridylamino functional group in molecules 1–3 are capable of chelating to metal ions such as Zn(II) as demonstrated by the synthesis and structure of the complex [2·(Zn(O2CCF3)2]2 (5). The binding of Zn(II) ions to the dipyridyl group causes a reduction of the emission efficiency of the ligand 2.

Blue organic light-emitting diodes based on Mes2B [p-4, 4' -biphenyl-NPh(1-naphthyl)]

Here, we report highly efficient blue organic light-emitting diodes (OLEDs) with Mes2B [p-4,4′-biphenyl-NPh(1-naphthyl)] (BNPB) as a blue emitter. It is found that both efficiencies and electroluminescent color are very sensitive to the selection of electron transport materials in the devices. For an optimized structure [indium tin oxide/2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (1nm)∕N,N′-di(naphthalen-1-yl)-N,N′-diphenyl-benzidine (45nm)/BNPB (20nm)/1,3,5-tris(2-N-phenylbenzimidazolyl) benzene (30nm)/LiF (1nm)/Al] with BNPB as an undoped blue emitter, a maximum current efficiency can reach 3.5cd∕A. It is found that BNPB emits two distinct peaks, one of around 450nm and the other of 485nm, and their respective emission intensities depend on the nature of majority charge carrier in the emission layer.