Backbone Tuning Enhances the Solution Aggregation to Refine Fibrillization Network Morphology for Efficient All-Chlorinated Polymer Donor

An ideal nanoscale interpenetrating network morphologythat isformed spontaneously upon a prepared active layer film is the keyto efficient exciton dissociation and charge transport. Here, a newstrategy is described for optimization of morphology by enhancingpolymer solution aggregation ability to effectively improve deviceperformance. Polymers PBDQx-Cl, PBDQx-TCl, and PBDQx-2TCl were designedand synthesized systematically by tuning the polymer backbones. Structuralmanipulation has been found to have a profound effect on the regulationof electronic structure and solution aggregation behavior. Comparedwith PBDQx-Cl and PBDQx-TCl, PBDQx-2TCl exhibits enhanced solutionaggregation ability and contributes to a fibrous phase separationin primitive pure film morphology. After blending with BTP-eC9, evolutionof a nanoscale fibrillization interpenetrating network morphologyis gradually demonstrated, in which the phase separation and microstructureform are collectively refined, which can provide more interface regionsand charge transport channels. The resulting PBDQx-2TCl:BTP-eC9 micromorphologicallymeets the requirements for efficient exciton splitting, charge transfer,and decreased recombination loss. Thus, among the three polymers,the device based on PBDQx-2TCl:BTP-eC9 shows the highest PCE of 16.17%with superior J (SC) of 26.49 mA cm(-2) and FF of 74.28%. These results demonstrate that the well-refinedfibrillar network morphology can be achieved by adjusting the aggregationability of a polymer solution. This in turn promotes a deeper understandingof the relationships between micromorphology and solution aggregationbehavior.