The present invention relates to a method of dedoping an organic semiconductor comprising the step of contacting a doped organic semiconductor with a compound of formula (1): ##STR00001## wherein R.sup.1-R.sup.8 each independently represents a hydrogen atom or a C.sub.1-C.sub.6 alkyl group which may be linear or branched and which may be optionally substituted with one or more hydroxyl groups and/or one or more halogen atoms and/or a C.sub.1-C.sub.3 alkoxy group; one or more pairs of R groups which are not hydrogen may join to form a cyclic group according to the following pairings: R.sup.1 and R.sup.2; R.sup.2 and R.sup.3; R.sup.3 and R.sup.4; R.sup.4 and R.sup.5; R.sup.5 and R.sup.6; R.sup.6 and R.sup.7; R.sup.7 and R.sup.8; and R.sup.8 and R.sup.1.