Investigations into the mechanism of recombination and trapping processes in modified polyfluorenes (PFs) were carried out in order to determine the influence of these phenomena on the electroluminescent properties of PF. The investigated polymers were PFs chemically substituted with triphenylamine derivatives (TPA) and contained from ca. 22 to ca. 75 wt.% of TPA side groups or a PF physically doped with 3 wt.% of a TPA derivative. For investigation of the trapping processes the thermoluminescence (TL) method with spectral analysis of the emitted light was applied. The TL measurements were carried out in the broad temperature range from liquid helium to room temperature. The physical doping and chemical modification of PF with TPA derivatives results in suppressing of the unwanted green emission in electroluminescence, what results most probably from an introduction of new trapping sites localized on the triphenylamine groups. In such systems the TPA groups, independently if chemically attached or molecularly dispersed, constitute the traps for holes, which effectively compete with the trapping sites responsible for green emission. The light emitting diodes (LEDs) built on polyfluorene system containing ca. 22 wt. % of triphenylamine groups show the best performances.

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