Semicrystalline D-A Copolymers with Different Chain Curvature for Applications in Polymer Optoelectronic Devices

Thiophene- and thienothiophene-based donor-acceptor (D-A) type semicrystalline copolymers with different backbone curvatures, PTBT14 and PTTBT14, were designed and synthesized. Both the polymers exhibit a nearly planar structure via noncovalent S center dot center dot center dot O and C-H center dot center dot center dot N attractive interactions, etc., in the polymer chain. PTTBT14 is linear, whereas PTBT14 is curved owing to similar to 160 degrees bond angle of the thiophene linkage. PTTBT14 showed the higher degree of interchain ordering with edge-on orientation, resulting in efficient charge transport (0.26 cm(2) V-1 s(-1) for PTTBT14 compared to 0.02 cm(2) V-1 s(-1) for PTBT14) in PFETs with remarkable morphological stability and no deterioration in device properties at temperatures up to 250 degrees C. On the other hand, the curved shape of PTBT14 attributed to its improved photovoltaic properties with a power conversion efficiency of 5.56%. The linear PTTBT14 showed much stronger self-interactions with negligible morphological changes and little miscibility with PC61BM, showing the poor photovoltaic characteristics.