Probing interfacial characteristics of rubrene/pentacene and pentacene/rubrene bilayers with soft X-ray spectroscopy.
The electronic structure of rubrene/pentacene and pentacene/rubrene bilayers has been investigated using soft X-ray absorption spectroscopy, resonant X-ray emission spectroscopy, and density-functional theory calculations. X-ray absorption and emission measurements reveal that it has been possible to alter the lowest unoccupied and the highest occupied molecular orbital states of rubrene in rubrene/pentacene bilayer. In the reverse case, one gets p* molecular orbital states originating from the pentacene layer. Resonant X-ray emission spectra suggest a reduction in the hole-transition probabilities for the pentacene/rubrene bilayer in comparison to reference pentacene layer. For the rubrenepentacene structure, the hole-transition probability shows an increase in comparison to the rubrene reference. We also determined the energy level alignment of the pentacene-rubrene interface by using X-ray and ultraviolet photoelectron spectroscopy. From these comparisons, it is found that the electronic structure of the pentacene-rubrene interface has a strong dependence on interface characteristics which depends on the order of the layers used.
Institute of Physics and Applied Physics, Yonsei University, Seoul, 120-749, Korea.
J H
JH
Seo
T M
TM
Pedersen
G S
GS
Chang
A
A
Moewes
K-H
KH
Yoo
S J
SJ
Cho
C N
CN
Whang
D004583:Electrons; D008422:Materials Testing; D008956:Models, Chemical; D009279:Naphthacenes / Q000737:chemistry*; D013052:Spectrometry, X-Ray Emission; D013057:Spectrum Analysis; D013499:Surface Properties; D014965:X-Rays
D009279:Naphthacenes; C045049:rubrene; C523499:pentacene