| abstract |
Spiro compounds of the formula (I), n where X 1 , X 2 , X 3 , X 4 are identical or different and are —S—, —O—, —NR 5 —, —CR 5 ═N— or —CR 5 ═CH—, with the proviso that at least one of the groups X 1-4 is different from —CR 5 ═CH—, are suitable as charge transport materials, in particular for photovoltaic cells, and as electroluminescence materials. |