Poly (2, 5-bis (2-octyldodecyl)-3, 6-di (furan-2-yl)-2, 5-dihydro-pyrrolo [3, 4-c] pyrrole-1, 4-dione-co-thieno [3, 2-b] thiophene): a high performance polymer semiconductor for both organic thin film transistors and organic photovoltaics