Fabrication and effect of the dielectric permittivity on the ideality factor of MEH-PPV Schottky diodes doped with electron acceptor fluorescent dyes

Polymeric Schottky diodes have been prepared using poly[2-methyl-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) conducting polymers. The I–V characteristics of these diodes are interpreted in terms of thermoionic emission (TIE) conduction process. Upon blending the polymer with Nile blue (NB) dye the conduction shows a cross-over from space-charge limited conduction (SCLC) to TIE at biasing voltages larger than 4 V. Disappearance of SCLC is seen in Rhodamine B (RhB)-based diodes and the conduction is interpreted in terms of the TIE process. Inclusion of the dielectric permittivity of the polymer/dye blends in interpreting the I–V characteristics of diodes is found to be crucial. A significant reduction of the ideality factor (n) from 6 to 1.8 is determined when MEH-PPV is mixed with NB or Rhodamine fluorescent dyes.