A process for preparing an aqueous or non-aqueous solution or dispersion of a polythiophene or thiophene copolymer, containing structural units according to formula (I): 1 in which R1 and R2 independently of one another represent hydrogen or a C1-5-alkyl group or together form an optionally substituted C1-5-alkylene residue, comprising the step of: preparing the polythiophene or thiophene copolymer with an initiator in a reaction medium in the presence of polyanions under oxidizing or reducing conditions under an inert atmosphere such that when said initiator is added less than 3 mg of oxygen per litre of the reaction medium is present in the reaction medium; an aqueous or non-aqueous solution or dispersion prepared therewith; the use of an aqueous or non-aqueous dispersion or solution comprising the aqueous or non-aqueous solution or dispersion of a polythiophene or thiophene copolymer for coating an object; a printable paste containing the aqueous or non-aqueous solution or dispersion of a polythiophene or thiophene copolymer; and an electroconductive or an antistatic layer prepared using an aqueous or non-aqueous solution or dispersion comprising the aqueous or non-aqueous solution or dispersion of a polythiophene or thiophene copolymer.