Band Formation at Interfaces Between N-Heteropolycycles and Gold Electrodes

Efficient charge injection at organic semiconductor/metal interfaces is crucial for the performance of organic field effect transistors. Interfacial hybrid band formation between electronic states of the organic compound and the metal electrode facilitates effective charge injection. Here, we show that a long-range ordered monolayer of a flat-lying N-heteropolycyclic aromatic compound on Au(111) leads to dispersing occupied and unoccupied interfacial hybrid bands. Using angle-resolved two-photon photoemission we determine their energy level alignment and dispersion relations. We suggest that band formation proceeds via hybridization of a localized occupied molecular state with the d-bands of the Au substrate, where the large effective mass of the d-bands is significantly reduced in the hybrid band. Hybridization of an unoccupied molecular state with the Au sp-band leads to a band with an even smaller effective mass.

Automated summary

Efficient charge injection at organic semiconductor/metal interfaces is crucial for organic field effect transistors. Hybrid band formation between electronic states of the organic compound and the metal electrode facilitates effective charge injection. Investigation on a long-range ordered monolayer of a flat-lying N-heteropolycyclic aromatic compound on Au(111) reveals dispersing occupied and unoccupied interfacial hybrid bands, with energy level alignment and dispersion relations determined using angle-resolved two-photon photoemission. The band formation is suggested to proceed via hybridization of localized occupied molecular state with d-bands of Au substrate, resulting in significantly reduced effective mass and an even smaller effective mass for unoccupied molecular state hybridizing with Au sp-band.