In Situ Structure Characterization in Slot‐Die‐Printed All‐Polymer Solar Cells with Efficiency Over 9%

Herein, high‐performance printed all‐polymer solar cells (all‐PSCs) based on a bulk‐heterojunction (BHJ) blend film are demonstrated using PTzBI as the donor and N2200 as the acceptor. A slot‐die process is used to prepare the BHJ blend, which is a cost‐effective, high‐throughput approach to achieve large‐area photovoltaic devices. The real‐time crystallization of polymers in the film drying process is investigated by in situ grazing incidence wide‐angle X‐ray scattering characterization. Printing is found to significantly improve the crystallinity of the polymer blend in comparison with spin coating. Moreover, printing with 1,8‐diiodooctane as the solvent additive enhances the polymer aggregation and crystallization during solvent evaporation, eventually leading to multi‐length‐scale phase separation, with PTzBI‐rich domains in‐between the N2200 crystalline fibers. This unique morphology achieved by printing fabrication results in an impressively high power conversion efficiency of 9.10%, which is the highest efficiency reported for printed all‐PSCs. These findings provide important guidelines for controlling film drying dynamics for processing all‐PSCs.