Résumé
ilole groups are known to present a high electron affinity. Initially, copolymn. of siloles with fluorene was aimed at improving electron injection into the polymer layer and so improving the electroluminescent properties of org. light-emitting diodes (OLED's) made from fluorene. But it also provides the ability to turn the light emission color to the green part of the spectrum and to stop the well-known spectral shift degrdn. occurring in fluorene-based materials. In this paper we report the synthesis and the characterization of 1,1-dimethyl-2,5-bis(fluoren-2-yl)-3,4-diphenylsilole 4, and of two sol. conjugated random copolymers derived from 9,9-ditetradecylfluorene and 1,1-dialkyl-2,5-diphenylsilole, where the alkyl group is either Me (11a) or n-hexyl (11b). Silole 4 crystallizes in the triclinic P-1 space group with a = 9.8771(8), b = 10.6240(10), c = 16.585(2) .ANG., a = 95.775(8), b = 97.025(7), and g = 111.738(8)°. The results obtained with this mol., operating in a single-layer OLED (luminance »450 Cd/m2 at 12 V; hmax = 0.2 Cd/A), give evidences for the complementarity of the silole and the fluorenyl moieties in the improvement of the charge injection processes when compared with 1,1-dimethyl-2,3,4,5-tetraphenylsilole. The results obtained from org. light-emitting electrochem. cells (LEC's) made from silole-fluorene copolymers 11a, 11b and molten salts show an improvement of both the device lifetime and the spectral stability when compared with polyfluorene. To explain devices performances elec. characterization data and at. force microscope (AFM) imaging were combined.