Chih-Hung Tsai

Stable styrylamine-doped blue organic electroluminescent device based on 2-methyl- 9,10-di(2-naphthyl)anthracene

We have developed a highly efficient and stable blue organic electroluminescent (EL) device based on a blue fluorescent styrylamine dopant, p-bis(p-N,N-diphenyl-aminostyryl)benzene, in a morphologically stable high band-gap host material, 2-methyl-9,10-di(2-naphthyl)anthracene, which achieved an EL efficiency of 9.7cd∕A and 5.5lm∕W at 20mA∕cm2 and 5.7 V, with Commission Internationale d’Eclairage coordinates of (x=0.16,y=0.32). The blue-doped device achieved a half-decay lifetime (t1∕2) of 46 000 h at an initial brightness of 100cd∕m2.

Highly efficient blue organic light-emitting devices incorporating a composite hole transport layer

Organic light-emitting devices (OLEDs) incorporating the copper phthalocyanine (CuPc)∕N,N′-bis-(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine composite hole transport layer have been fabricated. Under optimal condition, the highly efficient sky-blue OLED based on the aminosubstituted distyrylarylene fluorescent dye, doped in the stable diphenyanthracene blue host achieved a luminance efficiency of 16.2cd∕A with a Commission Internationale d’ Eclairage (CIE)x,y color coordinate of [0.15, 0.29] at 6.4V (20mA∕cm2) and an external quantum efficiency of 8.7%.

Highly stable organic light-emitting devices with a uniformly mixed hole transport layer

Highly stable organic light-emitting devices were made by using a uniformly mixed hole transport layer (UM-HTL) composed of a mixture of 2-methyl-9,10-di(2-naphthyl)anthracene (MADN) and N,N′-bis(1-naphthyl)-N,N′-diphenyl,1,1′-biphenyl-4,4′-diamine (NPB) in a 3:7 (MADN:NPB) ratio. The lifetime of 10-(2-benzothiazolyl)-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H,11H-benzo[l]-pyrano[6,7,8-ij]quinolizin-11-one doped green device with UM-HTL can be greatly improved to 2.7 times longer than that of the conventional device (NPB based HTL) without impacting on its driving voltage and emissive color significantly. This improvement in stability can be attributed to the fact that the unstable [Alq3+] species formed by electro-oxidation have been effectively suppressed.

Improved stability of organic electroluminescent devices by doping styrylamines in hole or electron transporting layer

The stability of green organic electroluminescent devices has been improved by doping styrylamine derivate, p-bis(p-N,N-diphenyl-aminostyryl)benzene (DSA-Ph) in hole or electron transporting layer. Compared with the undoped device, the stability of the electron transporting layer has increased by a factor of 1.8 without affecting the electroluminescence efficiency of 11cd∕A and color (CIEx,y=0.34, 0.62). The enhanced stability is believed to derive from the hole trapping nature of DSA-Ph which can reduce the residual hole carriers in tris(8-hydroquinolinato)aluminum (Alq3) and suppress the formation of fluorescent quencher of Alq3 cationic species.

P-115: Efficient Blue Organic Electroluminescent Devices Based on a Stable Blue Host Material

We have successfully synthesized a new blue host material, 2-methyl-9,10-di(2-napthyl)anthracene (MADN) which is highly stable in thin-film morphology comparing to the archetypical 9,10-di(2-napthyl)anthracene (ADN). When doped with 2,5,8,11-tetra(t-butyl)perylene (TBP) as blue emitter in organic light emitting device (OLED), MADN shows an improved EL efficiency of 4.4 cd/A and 2.2 lm/W at 20 mA/cm2 and 6.3 V with a CIEx, y coordinate of (0.14, 0.20). The blue device is stable with an extrapolated t1/2 ∼5000 h at an initial brightness of 880 cd/m2.

Effect of free electrons on nanoparticle charging in a negative direct current corona charger

A two-dimensional numerical model is proposed in this letter to take into account the effects of free electrons on nanoparticle charging in a negative direct current wire-tube corona charger. Numerical results are in excellent agreement with the experimental data by using a capturing probability of electrons onto nanoparticles with a value of 0.013. These free electrons contribute greatly to the charging efficiency at high products of mean ion concentration and mean residence time, which explains very well the large discrepancy found in earlier models that considered only negative ions.