Interdiffusion of molecular acceptors through organic layers to metal substrates mimics doping-related energy level shifts

Steffen Duhm, Ingo Salzmann, Benjamin Bröker, Hendrik Glowatzki, Robert L. Johnson, Norbert Koch
2009 Applied Physics Letters  
Photoemission measurements reveal energy level shifts toward the Fermi level when a strong electron acceptor ͑tetrafluoro-tetracyanoquinodimethane, F4-TCNQ͒ is deposited on pristine layers of 4,4Ј ,4Љ-tris͑N , N-diphenyl-amino͒triphenylamine ͑TDATA͒ or 4,4Ј-bis͑N-carbazolyl͒biphenyl ͑CBP͒. The shifts of the TDATA and CBP energy levels toward the Fermi level of the Au substrate could, in principle, arise from p-type doping of the intrinsic organic layers. While this indeed takes place in TDATA,
more » ... es place in TDATA, doping of CBP by F4-TCNQ, i.e., charge transfer complex formation, does not occur. The shifts observed in CBP arise from the diffusion of F4-TCNQ toward the Au substrate, which modifies the buried metal surface potential, leading to a realignment of the energy levels of the organic overlayer.
doi:10.1063/1.3213547 fatcat:kmccitqw4rasdh46ucsh5rspfe