Abstract: Provided is a process for preparing a composition comprising semiconducting single-walled carbon nanotubes, a semiconducting polymer and solvent A (composition A), which process comprises the step of separating composition A from a composition comprising semiconducting and metallic single-walled carbon nanotubes, the semiconducting polymer and solvent B (composition B), wherein the semiconducting polymer has a band gap in the range of 0.5 to 1.8 eV and solvent A and B comprise an aromatic or a heteroaromatic solvent, composition A itself, a process for forming an electronic device, which process comprises the step of forming a layer by applying composition A to a precursor of the electronic device, as well as the electronic device obtainable by this process.