Extremely low voltage organic light-emitting diodes with p -doped alpha-sexithiophene hole transport and n -doped phenyldipyrenylphosphine oxide electron transport layers

Organic light-emitting diodes with p -doped alpha-sexithiophene and n -doped phenyldipyrenylphosphine oxide carrier transport layers are fabricated. In the doped diodes, the authors demonstrate an extremely low driving voltage of 2.9 V at a current density of 100 mA cm2 and very high luminance at a low driving voltage: 1000 cd m2 at 2.4 V, 10 000 cd m2 at 2.8 V, and 920 000 cd m2 at 4.5 V. Such lowered driving voltages and enhanced luminance characteristics are attributed to the generation of free charge carriers by charge transfer from matrix to dopant molecules, resulting in an increase in electrical conductivities and formation of Ohmic contacts at metal/organic interfaces.