Improved Morphology and Interfacial Contact of PBDB-T:N2200-Based All-Polymer Solar Cells by Using the Solvent Additive p-Anisaldehyde

All-polymer solar cells (all-PSCs) have been intensively investigated due to their excellent thermal and mechanical stabilities. However, the efficiency of all-PSCs is still far behind that of organic solar cells (OSCs), which are based on small molecule acceptors. Improving the efficiency of all-PSCs is of great urgency. In this work, the solvent additive named p-anisaldehyde (AA) was introduced to improve the performance of all-PSCs based on PBDB-T:N2200. It is demonstrated that AA helps to form a better network interpenetrating track and more uniform phase separation. With the assistance of AA, which has both an oleophilic methoxy group and a hydrophilic aldehyde group, the interfacial contact between the donor and the acceptor (D/A) is improved, increasing the contact area at D/A and promoting efficient exciton dissociation. More importantly, AA acts as a “bridge” between the oleophilic active layer and the hydrophilic PEDOT:PSS layer, improving the interfacial compatibility between the active layer and the PEDOT:PSS layer, reducing the interfacial resistance, and facilitating the carrier transport. Finally, the all-PSCs based on PBDB-T:N2200 exhibits a superior power conversion efficiency (PCE) of 7.24% which is a record efficiency for the current all-PSCs with the same architecture. In this work, a promising and effective strategy for achieving high efficiency all-PSCs is provided.