Complex admittance measurements of polymer light-emitting electrochemical cells: Ionic and electronic contributions

Measurements of the frequency dependence of the complex admittance are used to separate the ionic and electronic contributions in polymer light-emitting electrochemical cells (LECs). At zero bias, a large polarizability, attributed to salt molecules in the electrolyte, is observed at low frequencies. Ions are generated when the LEC is biased at voltages above the threshold for electrochemical redox doping. Because of the slow ionic response, a novel pulsed drive scheme is proposed: the mean value stabilizes the induced p-i-n junction, while the peak value controls the carrier injection and the brightness of the electroluminescent emission. LECs operated in this way exhibit fast emissive response and improved operating life.

[1]  A. Heeger,et al.  Electrochemistry and electrogenerated chemiluminescence of films of the conjugated polymer 4-methoxy-(2-ethylhexoxyl)-2,5-polyphenylenevinylene , 1994 .

[2]  Qibing Pei,et al.  Imaging the structure of the p‐n junction in polymer light‐emitting electrochemical cells , 1996 .

[3]  Q. Pei,et al.  Planar light-emitting devices fabricated with luminescent electrochemical polyblends , 1997 .

[4]  Q. Pei,et al.  Light‐Emitting Electrochemical Cells with Crown Ether as Solid Electrolyte , 1997 .

[5]  D. Cahen,et al.  Analysis of light emitting polymer electrochemical cells , 1997 .

[6]  A. Jonscher.  The physical origin of negative capacitance , 1986 .

[7]  Ian H. Campbell,et al.  Electrical impedance measurements of polymer light-emitting diodes , 1995 .

[8]  Yang Yang,et al.  Efficient Photoluminescence and Electroluminescence from a Soluble Polyfluorene , 1996 .

[9]  Darryl L. Smith.  Steady state model for polymer light-emitting electrochemical cells , 1997 .

[10]  A. Heeger,et al.  Efficient, fast response light‐emitting electrochemical cells: Electroluminescent and solid electrolyte polymers with interpenetrating network morphology , 1996 .

[11]  Jun Gao,et al.  POLYMER LIGHT-EMITTING ELECTROCHEMICAL CELLS WITH FROZEN P-I-N JUNCTION , 1997 .

[12]  Mats Andersson,et al.  Polymer Light‐Emitting Electrochemical Cells with Frozen p‐i‐n Junction at Room Temperature , 1998 .

[13]  Yang Yang,et al.  Efficient blue-green and white light-emitting electrochemical cells based on poly[9,9-bis(3,6-dioxaheptyl)-fluorene-2,7-diyl] , 1997 .

[14]  A. Maradudin,et al.  Theory of dielectrics , 1949 .

[15]  A J Heeger,et al.  Polymer Light-Emitting Electrochemical Cells , 1995, Science.

[16]  Yang Yang,et al.  MEASUREMENT OF THE ENERGY GAP IN SEMICONDUCTING POLYMERS USING THE LIGHT-EMITTING ELECTROCHEMICAL CELL , 1996 .

[17]  A. Heeger,et al.  Cyclic Voltammetry Studies of Light‐Emitting Electrochemical Cells , 1997 .

[18]  A J Heeger,et al.  Polymer Light-Emitting Electrochemical Cells:  In Situ Formation of a Light-Emitting p-n Junction. , 1996, Journal of the American Chemical Society.

[19]  A. Heeger,et al.  ac impedance of polymer light-emitting electrochemical cells and light-emitting diodes: a comparative study , 1998 .