Morphology Control Realizes Fast Charge Dissociation and Transport in High-Performance All-Polymer Solar Cells

The difficulty in controlling the morphology of the active layer is a major factor for hindering the improvement of photovoltaic performance in all-polymer solar cells (all-PSCs). Here, we introduced two kinds of high-boiling-point solvent additives, 1,8-diiodooctane (DIO) and 1-chloronaphthalene (CN), to control the donor/acceptor blends, thereby improving the film formation and crystallization kinetics and molecular orientation of the active layer in all-PSCs. In this study, the effectiveness of high-boiling-point solvent additives in controlling the morphology of the active layer is examined. Moreover, it was found that the selectivity of additives affected the photovoltaic performance in all-PSCs, and improper additives could significantly reduce the power conversion efficiencies (PCEs). Through using an all-polymer system with D18-Cl as the polymer donor and PY-IT as the polymer acceptor, the CN-treated device exhibited poor PCE, while those employing DIO significantly improved the phase separation morphology of the active layer, resulting in an impressive PCE of 16.0%. Importantly, the DIO-treated device in the D18-Cl:PY-IT system could realize the faster charge dissociation and transport as well as lower bimolecular recombination. Furthermore, the corresponding devices exhibited excellent storage stability, retaining over 80% of their initial efficiency after 3000 h in a nitrogen-atmosphere glovebox, which was potentially beneficial for the future commercial application.