A polymer blend includes an organic semiconductor polymer blended with an isolating polymer; at least one photoinitiator for generating active radicals; and at least one crosslinker comprising C═C bonds, thiols, or combinations thereof, such that the organic semiconductor polymer is a diketopyrrolopyrrole-fused thiophene polymeric material, the fused thiophene is beta-substituted, and the isolating polymer has a non-conjugated backbone. A method of forming an organic semiconductor device having the polymer blend is also presented.