Hole injection barriers at polymer anode/small molecule interfaces

A photoemission study of the interface between spin-cast films of a conducting polymer blend consisting of poly(3,4-ethylenedioxythiophene) (PEDOT), poly(4-styrenesulfonate) (PSS) and glycerol as an additive, and vacuum-evaporated hole transport layers (HTL) of 4,4′-bis(carbazol-9-yl)biphenyl, N,N′-diphenyl-N,N′-bis(1-naphthyl)-1-1′biphenyl-4,4′-diamine and N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′- biphenyl-4,4′-diamine reveals a hole injection barrier between 0.5 and 0.9 eV at the glycerol-modified PEDOT-PSS/HTL interface. The measured energy barriers imply a reasonable charge injection, which is very encouraging for further development of the novel anode structures based on a conducting polymer/small molecule interface to be utilized in electro-optic applications such as organic light-emitting devices.

[1]  Antti J. Maekinen,et al.  Femtosecond photoemission study of excited state dynamics in organic photoreceptors , 2000, Photonics West - Optoelectronic Materials and Devices.

[2]  Eric W. Forsythe,et al.  Interface formation between NPB and processed indium tin oxide , 2000 .

[3]  W. R. Salaneck,et al.  Polymer band alignment at the interface with indium tin oxide: consequences for light emitting devices , 1999 .

[4]  William R. Salaneck,et al.  Electronic structure of hybrid interfaces of poly(9,9-dioctylfluorene) , 2000 .

[5]  K. Seki,et al.  Energy level alignment at organic/metal interfaces studied by UV photoemission: breakdown of traditional assumption of a common vacuum level at the interface , 1997 .

[6]  Alan J. Heeger,et al.  Polymer light-emitting diodes with polyethylene dioxythiophene–polystyrene sulfonate as the transparent anode , 1997 .

[7]  Damodar M. Pai,et al.  Hole transport in solid solutions of a diamine in polycarbonate , 1984 .

[8]  Yang Yang,et al.  Carrier injection into semiconducting polymers: Fowler-Nordheim field-emission tunneling , 1994 .

[9]  W. R. Salaneck,et al.  Energy level alignment in organic-based three-layer structures studied by photoelectron spectroscopy , 2000 .

[10]  Marie Angelopoulos,et al.  Polymeric anodes for improved polymer light-emitting diode performance , 1997 .

[11]  S. Karg,et al.  Polymeric anodes for organic light-emitting diodes , 1997 .

[12]  Siegfried Karg,et al.  Increased brightness and lifetime of polymer light-emitting diodes with polyaniline anodes , 1996 .

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

[14]  A. J. Heeger,et al.  Polyaniline as a transparent electrode for polymer light‐emitting diodes: Lower operating voltage and higher efficiency , 1994 .