A polymer comprising one or more types of repeat units, wherein the polymer includes a substituted thieno[3,2-b]thiophene component A and a different component B in the same type of repeat unit or in different types of repeat units, and wherein the polymer excludes a substituted or unsubstituted thieno[2,3-b]thiophene moiety. The polymer can be used as a semiconductor in electronics such as in organic thin film transistors.