title: Electronic structure of NPB and BCP molecules probed by x-ray emission spectroscopy.
abstract: Soft x-ray absorption and emission spectroscopies have been employed to investigate the electronic structure and chemical bonding of two prototypical molecules, N,N(')-bis-(1-naphthyl)-N,N(')-diphenyl-1,1(')-biphenyl-4,4(')-diamine (NPB) and bathocuproine (BCP), which are frequently chosen because of their hole-transporting and hole-blocking properties, respectively. The resulting resonant C Kalpha x-ray emission spectra of these materials reveal different spectral features depending on the resonant excitation energy. According to the N absorption and emission spectra, the contribution of N atoms to the highest occupied and lowest unoccupied molecular orbitals is different for in NPB and in BCP. Detailed knowledge of these materials will allow tailoring charge transport properties of organic devices in order to develop high performance organic light-emitting diodes and photovoltaic cells.
authors.affiliation: Institute of Physics and Applied Physics, Yonsei University, Seoul 120-749, Korea.
authors.forename: J H
authors.initials: JH
authors.lastname: Seo
authors.forename: C Y
authors.initials: CY
authors.lastname: Kim
authors.forename: S J
authors.initials: SJ
authors.lastname: Kang
authors.forename: K-H
authors.initials: KH
authors.lastname: Yoo
authors.forename: C N
authors.initials: CN
authors.lastname: Whang
authors.forename: A
authors.initials: A
authors.lastname: Moewes
authors.forename: G S
authors.initials: GS
authors.lastname: Chang