Organic electroluminescent (EL) devices have attracted much attention because of their high potential for full-color large-area flat panel display applications. One of the important steps for full color displays is the realization of red electroluminescence (EL). Porphyrin compounds have many derivatives that have various molecular structure and electronic states

including PtOEP

TPP

ZnTPP ect.

which were used for red-emitting materials.In this paper

a new compound 2

3

7

8

12

13

17

18-octaethyl-21H23H-porpine zinc (ZnOEP) was proposed for red electroluminescence. Organic EL devices with ZnOEP as a dopant at various concentrations within a tris (8-hydroxyquinoline) aluminum (Alq

3

) host layer were prepared by conventional vapor deposition. The multi layer structure of the devices is ITO/TPD/ZnOEP:Alq

3

/Alq

3

/Mg:Ag.For deposition of the ZnOEP:Alq

3

layer

the evaporation rates for the ZnOEP dopant and the Alq

3

host were independently controlled by separate thin film deposition monitor.The dopant concentrations in the Alq

3

were 0.5

2

10 and 15wt%

respectively. EL spectra

B-J

curves and pulse response characteristics of the devices were measured. It was found that EL spectra and

B-J

curves were significantly different as the dopant concentration varied.In the spectra of all the devices

there were two peaks at about 590nm and 630nm

which were originate from ZnOEP molecular excitons.It is observed that the peak at 590nm becomes weaker when the ZnOEP dopant concentration increases and the emission color turns from orange to red

while the luminance efficiency drops from 0.96cd/A to 0.14cd/A.The experimental results may be explained by the following two factors:the self absorption of ZnOEP and the phenomena of concentrated quenching. Additionally

response time characteristics were obtained by measuring the EL light waveforms while using rectangular voltage pulses of 100s duration. The pulse response characteristic of the device may indicate the existence of the energy transfer between the Alq

3

and the ZnOEP molecules. In conclusion

it is the first time to get electroluminescence from ZnOEP:Alq

3

system in this paper.The EL spectra of the devices changed with the ZnOEP dopant concentration due to the self absorption of ZnOEP and the phenomena of concentrated quenching.When the ZnOEP dopant concentration is over 10%

red electroluminescence was obtained.In additional

the pulse response characteristics of the devices were investigated

too.