Wavelength (nm)

Figure 9. Electroluminescence spectra of 4a-d (generation 0-3) and solution photoluminescence (dotted line), which does not depend on the generation. Reprinted with permission from [42], J. M. Lupton et al., Adv. Mater. 13, 258 (2001). © 2001, Wiley-VCH.

increases. It turned out that the charge transport is essentially determined by the core. The main role of the dendrons in 4a-d consists of the spacing of the core chromophores, which grows with growing numbers n [42].

The ITO-Ca device used for the single-layer dendrimers 5b-d gave broad electroluminescence emission bands with quantum yields between 20 and 36%. The external quantum efficiencies were measured between 0.01 and 0.09%. A systematic change with the generation could not be found. All three investigated compounds of the series proved to be suitable for an application in LEDs; the best results were obtained for 5c.

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