Very low voltage and stable p-i-n organic light-emitting diodes using a linear S,S-dioxide oligothiophene as emitting layer

Very low voltage organic light-emitting diodes using a fluorescent linear S,S-dioxide oligothiophene as emitting layer has been realized using a p-i-n structure. The device reaches a remarkable luminance of 10 000 cd/m2 at only 9 V, which is two orders of magnitude higher than the simple bilayer structure already reported for this active material. Due to the doping of the transport layers, a maximum power efficiency of 2.1 lm/W was reached against 0.2 lm/W of the corresponding undoped device. As a consequence of this higher power efficiency, the reduced self-heating of the p-i-n device structure, compared to the undoped devices, determines the best operating condition to check the intrinsic stability of the emitting layer. Aging measurements reveal indeed a very high stability, with extrapolated device lifetimes at about 10 8 and 2200 h at starting luminances of 100 and 3200 cd/m2 , respectively.