First principle calculations have been performed to study the carrier type and transport characteristics of unsubstituted and substituted S,N-heteroacene molecules with different conjugation lengths. It has been revealed that the unsubstituted conjugated heteroacenes are mainly hole conducting while substitution at both ends by strong electron withdrawing dicyanovinylene (DCV) groups turn them into electron conducting materials. This opens an easy possibility of obtaining pair of hole and electron transporting materials in the series of S,N-heteroacenes by simple chemical functionalization.