Effects of annealing of poly(3-hexylthiophene) film on the performance of double-layered EL devices of ITO/polymer/Alq3/Mg-Ag

Ohshita Joji

Tada Yosuke

Kunai Atsutaka

Harima Yutaka

Kohno Atsushi

Kunugi Yoshihito

Synthetic Metals

Double layer devices with a structure of ITO/pHT/Alq3/Mg-Ag (ITO = indium tin oxide, pHT = regio-regular or random poly(3-hexylthiophene), Alq3 = tris(8-hydroxyquinoline)aluminium) were fabricated. The device with a random pHT film emitted a green-yellow light in all voltage region, while that having a regio-regular pHT film exhibited a color change from green to red by applying the bias voltage higher than 15 V. Annealing the pHT films prepared on ITO at 200 °C for 1 h in nitrogen, prior to vapor-deposition of the Alq3 layer, improved the device performance with lowering the onset bias voltage by 2-3 V. The EL colors and spectra were also affected by annealing. X-ray reflectivity measurements before and after annealing the pHT film on ITO indicated increased density of the pHT layer and structural changes in the pHT/ITO interface by annealing, which seems to be responsible for the improved EL device performance

Annealing

EL device

Hole-transport

Interface

Polythiophene

Regio-regularity

X-ray reflectivity

Chemistry [ 430 ]

eng

Elsevier Science SA

Copyright(c) 2007 Elsevier Science SA

[ISSN] 0379-6779

[DOI] 10.1016/j.synthmet.2006.12.009

[NCID] AA00446016

[DOI] http://dx.doi.org/10.1016/j.synthmet.2006.12.009 isVersionOf