Multiple conformation locks gift polymer donor high efficiency

The mechanism that how noncovalent conformation locks (NCLs) to improve the photovoltaic performance of polymer donors was investigated. By developing a model system with three structure-related copolymers W1, W2 and W3, a clear correlation was found between the locking strength in polymer backbone and the photovoltaic performance. W1 with the strongest S⋅⋅⋅O and F⋅⋅⋅H double-side locking gave the highest power conversion efficiency (PCE) of 16.23%, while W2 with a S⋅⋅⋅O single-side locking and W3 with a weakened S⋅⋅⋅O locking caused by Cl–H steric repulsion gave lower PCEs of 11.73% and 0.92%, respectively. With the aid of single crystal X-ray diffraction analysis, density functional theory calculation, grazing-incidence wide-angle X-ray scattering analysis, atomic force microscope study and device characterization, the functions of NCLs in improving the planarity, packing, crystallinity and hole mobility of polymers, as well as the morphology of blend films, were illuminated in detail.