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Neat Alq3 thin film and metal/Alq3 interfaces studied by NEXAFS spectroscopy

2005; Elsevier BV; Volume: 152; Issue: 1-3 Linguagem: Inglês

10.1016/j.synthmet.2005.07.108

1879-3290

Takahiro Yokoyama, Hisao Ishii, Noritaka Matsuie, Kaname Kanai, Eisuke Ito, Atsuhiro Fujimori, Tohru Araki, Yukio Ouchi, Kazuhiko Seki,

Organic Electronics and Photovoltaics

Thin film of Alq3 and its interfaces with various metals (K, Li, Ca, Al)/Alq3 and the Al/LiF/Alq3 interface were investigated using NEXAFS spectroscopy. The assignments of structures in NEXAFS spectra at the C, N and O K-edges were performed using theoretical calculations taking account of the core-excitonic effect. The NEXAFS spectra at the three edges are well reproduced by the simulated results. The spectra at the N and O K-edges of Alq3 are similar to the partial density of unoccupied states (PDOUS) of the ground state, but the spectrum at the C K-edge is different from the PDOUS of ground state due to the core-excitonic effect. The present study is the first trial of the detailed analysis of the C K-edge spectrum of Alq3. The spectral changes at the metal/Alq3 and Al/LiF/Alq3 interface were found to depend on the metal. By the comparison with the theoretical simulations based on the 1:1 metal-Alq3 complex, we found that the electron transfer and orbital overlap occur at the interfaces of K/Alq3 and Li/Alq3, while the observed changes at the Ca/Alq3 and Al/Alq3 interfaces could not be understood by the simulated results. At the LiF/Alq3 interface, we observed the spectral changes which may result from some chemical interaction. Some of the spectral changes at Al/LiF/Alq3 interface differ from those of Al/Alq3 interface, indicating chemical interaction specific for the co-existence of Al, LiF, and Alq3.