Controlled p-doping of zinc phthalocyanine by coevaporation with tetrafluorotetracyanoquinodimethane: A direct and inverse photoemission study

P-doping of zinc phthalocyanine (ZnPc) with tetrafluorotetracyanoquinodimethane (F4-TCNQ) is investigated with ultraviolet and x-ray photoemission spectroscopy, inverse photoemission spectroscopy, and in situ current–voltage (I–V) measurements. The electron affinity of F4-TCNQ (5.24 eV) is found to be equal, within experimental error, to the ionization energy of ZnPc (5.28 eV), consistent with efficient host-to-dopant electron transfer. As a result, the Fermi level in doped ZnPc drops from near midgap to 0.18 eV above the leading edge of the highest occupied molecular orbital and a narrow space-charge layer (<32 A) is formed at the interface with the Au substrate. In situ I–V measurements show a seven orders of magnitude doping-induced increase in hole current.

[1]  Xiang Zhou,et al.  Very-low-operating-voltage organic light-emitting diodes using a p-doped amorphous hole injection layer , 2001 .

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

[3]  N. Koch,et al.  Bipolaron: The Stable Charged Species in n-Doped p-Sexiphenyl , 2000 .

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

[5]  A. Beyer,et al.  Controlled doping of molecular organic layers: Physics and device prospects , 1999 .

[6]  A. Kahn,et al.  Electronic structure, diffusion, and p-doping at the Au/F16CuPc interface , 2001 .

[7]  Robert A Norwood,et al.  CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES 3202 Controlled doping of phthalocyanine layers by cosublimation with acceptor molecules: A systematic Seebeck and conductivity study , 1998 .

[8]  Martin Pfeiffer,et al.  Interface electronic structure of organic semiconductors with controlled doping levels , 2001 .

[9]  Martin Pfeiffer,et al.  LOW VOLTAGE ORGANIC LIGHT EMITTING DIODES FEATURING DOPED PHTHALOCYANINE AS HOLE TRANSPORT MATERIAL , 1998 .

[10]  Kazuhiko Seki,et al.  Electronic structures of organic molecular materials for organic electroluminescent devices studied by ultraviolet photoemission spectroscopy , 1998 .

[11]  H. Sirringhaus,et al.  Electron-hole interaction energy in the organic molecular semiconductor PTCDA , 1997 .

[12]  K. Seki,et al.  Polarization energies of organic solids determined by ultraviolet photoelectron spectroscopy , 1981 .

[13]  A. Kahn,et al.  Energy-level alignment at interfaces between metals and the organic semiconductor 4,4′-N,N′-dicarbazolyl-biphenyl , 1998 .

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

[15]  K. Leo,et al.  Controlled n-type doping of a molecular organic semiconductor: Naphthalenetetracarboxylic dianhydride (NTCDA) doped with bis(ethylenedithio)-tetrathiafulvalene (BEDT-TTF) , 2000 .

[16]  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 .

[17]  G. Pourtois,et al.  The influence of the counterion on the electronic structure in doped phenylene-based materials , 2000 .

[18]  M. Fujihira,et al.  Improved drive voltages of organic electroluminescent devices with an efficient p-type aromatic diamine hole-injection layer , 2000 .