The role of interface states in controlling the electronic structure of Alq3/reactive metal contacts

Abstract Gap states induced by the formation of metal/organic interfaces have been observed in a number of instances. Yet, the role that these states play in determining the electronic structure of the interface and the carrier injection barriers has not been clearly established. In this paper, we provide a model for the role of chemistry-induced gap states at Mg/Alq3 and Al/Alq3 interfaces, in particular with regard to the formation of dipole barrier and level bending. We show that these states play a defining role in producing identical Fermi level positions at metal-on-organic and organic-on-metal interfaces. The model is supported by photoemission and current–voltage measurements.

[1]  N. Koch,et al.  Bipolaron formation in para-sexiphenyl thin films upon Cs doping , 2000 .

[2]  Shui-Tong Lee,et al.  Energy level alignment at Alq/metal interfaces , 1998 .

[3]  Shui-Tong Lee,et al.  Theory of magnesium/Alq3 interaction in organic light emitting devices , 1999 .

[4]  A. Kahn,et al.  Chemical and electrical properties of interfaces between magnesium and aluminum and tris-(8-hydroxy quinoline) aluminum , 2001 .

[5]  J. H. Weaver.  Electronic structures of C60, C70 and the fullerides: Photoemission and inverse photoemission studies , 1992 .

[6]  A. Kahn,et al.  Metal-dependent charge transfer and chemical interaction at interfaces between 3,4,9,10-perylenetetracarboxylic bisimidazole and gold, silver and magnesium , 2000 .

[7]  A. Kahn,et al.  Photoemission spectroscopy investigation of magnesium–Alq3 interfaces , 1998 .

[8]  Kahn,et al.  Chemistry and electronic properties of metal-organic semiconductor interfaces: Al, Ti, In, Sn, Ag, and Au on PTCDA. , 1996, Physical review. B, Condensed matter.

[9]  W. R. Salaneck,et al.  Electronic structure of tris(8-hydroxyquinoline) aluminum thin films in the pristine and reduced states , 1999 .

[10]  N. Ueno,et al.  Origin of indium-[perylene-3,4,9,10-tetracarboxilic dianhydride] interface states studied by outermost surface spectroscopy using metastable atoms , 2001 .

[11]  Yongli Gao,et al.  Investigation of the interface formation between calcium and tris-(8-hydroxy quinoline) aluminum , 1998 .

[12]  Antoine Kahn,et al.  Charge-separation energy in films of π-conjugated organic molecules , 2000 .

[13]  K. Seki,et al.  ENERGY LEVEL ALIGNMENT AND INTERFACIAL ELECTRONIC STRUCTURES AT ORGANIC/METAL AND ORGANIC/ORGANIC INTERFACES , 1999 .

[14]  Antoine Kahn,et al.  Molecular level alignment at organic semiconductor-metal interfaces , 1998 .

[15]  Alessandro Curioni,et al.  Metal−Alq3 Complexes: The Nature of the Chemical Bonding , 1999 .

[16]  Stephen R. Forrest,et al.  Lithium doping of semiconducting organic charge transport materials , 2001 .

[17]  Chongfei Shen,et al.  Organometallic Chemistry at the Magnesium- Tris(8-hydroxyquinolino)aluminum Interface , 2000 .