Anode Interfacial Engineering Approaches to Enhancing Anode/Hole Transport Layer Interfacial Stability and Charge Injection Efficiency in Organic Light-Emitting Diodes

Abstract

The integrity of anode/organic interfacial contact is shown to be crucial to the performance and stability of archetypical small molecule organic light-emitting diodes (OLEDs). In this contribution, vapor-deposited lipophilic, hole-transporting 1,4-bis(phenyl-m-tolylamino)biphenyl (TPD) and 1,4-bis(1-naphthylphenylamino)biphenyl (NPB) thin films are shown to undergo decohesion on ITO anode surfaces under mild heating. An effective approach to ameliorate such interfacial decohesion is introduction, via self-assembly or spin-coating, of covalently bound N(p-C6H4CH2CH2CH2SiCl3)3 (TAA)- and 4,4‘-bis[(p-trichlorosilylpropylphenyl)phenylamino]biphenyl (TPD-Si2)-derived adhesion/injection layers at the anode/hole transport layer interface. The resulting angstrom-scale hole transport layers prevent decohesion of vapor-deposited hole transport layers and significantly enhance OLED hole injection fluence. OLEDs fabricated with these modified interfaces exhibit appreciably reduced turn-on voltages, considerably high...