PDT‐S‐T: A New Polymer with Optimized Molecular Conformation for Controlled Aggregation and π–π Stacking and Its Application in Efficient Photovoltaic Devices

The correlation among molecular conformation, the crystallinity of the morphology, propensity for π-π stacking, J- versus H-aggregation, and photovoltaic performance have been studied based on two newly designed polymers, PBDTTT-S-T and PDT-S-T. The results show that more linear backbone structure is helpful to improve photovoltaic properties of the polymer, and therefore, molecular conformation should be considered for molecular design of photovoltaic polymers.