Influence of emission sites on emission efficiency and running durabil
ity of molecular organic electroluminescent devices was investigated.
When fluorescent dye rubrene was doped into TPD diamine hole transport
layer, rubrene molecule emitted bright yellow light with a max. lumin
ance of 61 000 cd/m(2). The device had the highest efficiency of 9.8 l
m/W at 100 cd/m(2). Half-decay time of the device from initial luminan
ce of 530 cd/m(2) under constant direct current was 3 600 h. On the ot
her hand, when rubrene was doped into BeBq(2) complex electron transpo
rt layer, the efficiency was 4.4 Im/W and the half-decay time was 110
h. Thus doping site is found to exert significant influence both on th
e emission efficiency and the running durability.