Revealing the Molar Mass Dependence on Thermal, Microstructural,and Electrical Properties of Direct Arylation PolycondensationPrepared Poly(3-hexylthiophene)

Poly(3-hexylthiophene) (P3HT) is a"fruitfly"conjugatedpolymer in thefield of organic electronics due to its simple chemical structure,decent photoelectric properties, and low cost. To date, the design ofnonfullerene acceptors matching P3HT and the synthesis of high-qualityP3HT via sustainable methods hold tremendous promises for advancing theP3HT solar cells. The use of P3HT via direct arylation polycondensation(DArP) has recently proven to be an efficient means for constructing efficientpolythiophene solar cells, while the intrinsic properties of DArP prepared P3HTremain poorly understood, thus impeding further performance enhancements.Herein, six batches of P3HTs with weight-average molecular weights from 8.5 to73.9 kg/mol were successfully synthesized via DArP, and multitechniquecharacterizations were employed to investigate the molecular weight effect ofP3HT on its optical properties, crystallization behaviors, morphology, and electrical properties. P-52k with relatively highcrystallinity and hole mobility was applied in photovoltaic devices matching a variant of the popular nonfullerene acceptor Y6. Thisphotovoltaic combination afforded a good power conversion efficiency of over 7% in P3HT/nonfullerene solar cells. Importantly,this research not only provides insights into the physical properties of DArP prepared P3HT as a function of molecular weight butreveals the correlation between the key structure parameter and the electrical performance of P3HT for optoelectronic applicationsas well.