Low pressure organic vapor phase deposition of small molecular weight organic light emitting device structures

A new technique for the deposition of amorphous organic thin films, low pressure organic vapor phase deposition (LP-OVPD), was used to fabricate organic light emitting devices (OLEDs) consisting of a film of aluminum tris-(8 hydroxyquinoline) $({\mathrm{Alq}}_{\mathrm{3}})$ grown on the surface of a film of $N^{\prime }-\mathrm{diphenyl}{\mathrm{-N,N}}^{\prime }-{\mathrm{bis(3-methylphenyl)1-1}}^{\mathrm{\prime }}{\mathrm{biphenyl-4-4}}^{\mathrm{\prime }}\mathrm{diamine}.$ The resulting heterojunction OLED was found to have a performance similar to conventional, small molecular weight OLEDs grown using thermal evaporation in vacuum. The LP-OVPD grown device has an external quantum efficiency of $\text{0.40±0.05\%}$ and a turn-on voltage of approximately 6 V. The rapid throughput demonstrated with LP-OVPD has the potential to facilitate low cost mass production of conventional small molecule based OLEDs, and its use of low vacuum in a horizontal reactor lends itself to roll-to-roll deposition of organic films for many photonic device applications.