Energy Transfer within Mixed Phase Polyfluorene Based Phosphorescent Electroluminescent Devices

• Published in: Journal of physical chemistry. C 2012-02, Vol.116 (6), p.4259-4266
• Main Authors: Gutiérrez-Llorente, Araceli, Arredondo, B, Romero, B
• Format: Article
• Language: English
• Subjects: Applied sciences; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electroluminescence; Electronics; Exact sciences and technology; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optoelectronic devices; Other luminescence and radiative recombination; Physics; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp209531j

The fraction of β chains is expected to have a strong influence on the energy transfer processes in organic light-emitting diodes based on mixed phase polyfluorene doped with transition metal phosphors. Here, we report on the electroluminescence emission properties of devices based on poly(9,9-dioctylfluorene), containing different fractions of β phase, doped with varying ratios of an iridium triplet emitter. We measure the electroluminescence spectra at constant current density and the current density–voltage characteristics of the diodes. We also investigate the temperature dependence of electroluminescence emission within a temperature range between 77 and 270 K in this system. For a given dopant concentration and β phase content, the electroluminescent emission covers a broad range of the spectrum. Trap-assisted recombination in β phase sites, which act as electron trapping sites, would compete with direct charge recombination in dopant sites, which might act as a hole trap. Singlet energy transfer seems also to contribute to the excitation of the phosphors in doped devices.