Theoretical design of new cyclopentadithiophene-based organic semiconductors with tunable nature and performance.

• Eight β-diphenyl substituted cyclopentadithiophene (CPD) derivatives with C s and C 2 symmetry and four unsubstituted CPDs were designed. • Different roles of phenyl, fluorine, and dicyanomethylene substitution, the α and β positions of phenyl on the thiophene ring were revealed. • Single-crystal structure of CPD derivatives was predicted theoretically. • Reorganization energies, charge transfer integrals, charge carrier mobilities were systematically studied. • Semiconductor nature and performance could be tuned upon molecule design. Eight cyclopentadithiophene (CPD) based semiconductors are designed by moving phenyl/fluorine-phenyl groups from α to β positions of thiophenes of CPD. The semiconductor performances of these CPD derivatives with Cs and C 2 symmetry (termed as CPD' and CPD", respectively) and their unsubstituted CPD backbones are analyzed systematically through DFT calculations. Some CPD'/CPD" compounds show better charge transfer mobility than CPD. We analyze in detail the factors influencing the semiconductor nature of these CPD derivatives and their charge carrier mobilities, revealing the different roles of fluorine and dicyanomethylene and of the α and β position of phenyl on the thiophene rings. Our findings can be generalized to broader classes of organic semiconductors and are expected to contribute to the rational design of n-type semiconductors based on CPDs. [ABSTRACT FROM AUTHOR]